Surface acoustic wave device

A surface including interdigital electrode on the surface thereof, which is reduced in size and improved in selectivity, and has a broad band. To achieve this, a langasite single crystal belonging to a point group 32 is first used for the substrate. Secondly, I. a piezoelectric film is provided for covering the surface of the substrate and the surface of the interdigital electrode, II. a piezoelectric film is provided on the surface of the substrate and the interdigital electrode is provided on the surface of the piezoelectric film, III. a piezoelectric film is provided for covering the surface of the substrate and the surface of the interdigital electrode and an opposite electrode film is provided on the surface of the piezoelectric film, or IV. an opposite electrode film is provided on the surface of the substrate, a piezoelectric film is provided on the opposite electrode film and the interdigital electrode is provided on the surface of the piezoelectric film. The piezoelectric film is made up of zinc oxide, and has a piezoelectric axis oriented substantially perpendicularly with respect to the surface of the substrate. The cut angle of the substrate cut out of the langasite single crystal, the propagation direction of surface acoustic waves on the substrate, and the thickness of the piezoelectric film are optimized depending on how to provide the piezoelectric film.

What we claim is:

1. A surface acoustic wave device, comprising:

a substrate,

an interdigital electrode on a surface of said substrate, and

a piezoelectric film configured to cover said surface of said substrate and a surface of said interdigital electrode, wherein:

said substrate is a langasite single crystal belonging to a point group 32, and when a cut angle of said substrate cut out of the langasite single crystal and a propagation direction of surface acoustic waves on said substrate are represented in terms of Euler angles (.phi., .theta., .psi.), where

-5.degree..ltoreq..phi..ltoreq.5.degree.

85.degree..ltoreq..theta..ltoreq.95.degree.

-90.degree..ltoreq..psi.<-70.degree., and

said piezoelectric film is a c-axis oriented ZnO film that satisfies:

h/.lambda.=0.2 to 0.8

where h is a thickness of said ZnO film, and .lambda. is a wavelength of a surface acoustic wave.

2. A surface acoustic wave device comprising:

a substrate,

an interdigital electrode on a surface of said substrate, and

a piezoelectric film configured to cover said surface of said substrate and a surface of said interdigital electrode, wherein:

said substrate is a langasite single crystal belonging to a point group 32, and when a cut angle of said substrate cut out of the langasite single crystal and a propagation direction of surface acoustic waves on said substrate are represented in terms of Euler angles (.phi., .theta., .psi.), where

-5.degree..ltoreq..phi..ltoreq.5.degree.

85.degree.>.theta..ltoreq.95.degree.

-70.degree..ltoreq..psi.<-50.degree., and

said piezoelectric film is a c-axis oriented ZnO film that satisfies:

h/.lambda.=0.25 to 0.7

where h is a thickness of said ZnO film, and .lambda. is a wavelength of a surface acoustic wave.

3. A surface acoustic wave device comprising:

a substrate,

an interdigital electrode on a surface of said substrate, and

a piezoelectric film configured to cover said surface of said substrate and a surface of said interdigital electrode, wherein:

said substrate is a langasite single crystal belonging to a point group 32, and when a cut angle of said substrate cut out of the langasite single crystal and a propagation direction of surface acoustic waves on said substrate are represented in terms of Euler angles (.phi., .theta., .psi.), where

5.degree..ltoreq..phi..ltoreq.5.degree.

85.degree..ltoreq..theta..ltoreq.95.degree.

-50.degree..ltoreq..psi.<-35.degree., and

said piezoelectric film is a c-axis oriented ZnO film that satisfies:

h/.lambda.=0.25 to 0.45

where h is a thickness of said ZnO film, and .lambda. is a wavelength of a surface acoustic wave.

4. A surface acoustic wave device comprising:

a substrate,

an interdigital electrode on a surface of said substrate, and

a piezoelectric film configured to cover said surface of said substrate and a surface of said interdigital electrode, wherein:

said substrate is a langasite single crystal belonging to a point group 32, and when a cut angle of said substrate cut out of the langasite single crystal and a propagation direction of surface acoustic waves on said substrate are represented in terms of Euler angles (.phi., .theta., .psi.), where

-.degree..ltoreq..phi..ltoreq. .degree.

85.degree..ltoreq..theta..ltoreq.95.degree.

35.degree..ltoreq..psi.<-25.degree., and

said piezoelectric film is a c-axis oriented ZnO film that satisfies:

0<h/.lambda..ltoreq.0.5

where h is a thickness of said ZnO film, and .lambda. is a wavelength of a surface acoustic wave.

5. A surface acoustic wave device comprising:

a substrate,

an interdigital electrode on a surface of said substrate, and

a piezoelectric film configured to cover said surface of said substrate and a surface of said interdigital electrode, wherein:

said substrate is a langasite single crystal belonging to a point group 32, and when a cut angle of said substrate cut out of the langasite single crystal and a propagation direction of surface acoustic waves on said substrate are represented in terms of Euler angles (.phi., .theta., .psi.), where

-5.degree..ltoreq..phi..ltoreq.5.degree.

85.degree..ltoreq..theta..ltoreq.95.degree.

-25.degree..ltoreq..psi..ltoreq.-10.degree., and

said piezoelectric film is a c-axis oriented ZnO film that satisfies:

0<h/.lambda..ltoreq.0.45

where h is a thickness of said ZnO film, and .lambda. is a wavelength of a surface acoustic wave.

6. A surface acoustic wave device comprising:

a substrate,

an interdigital electrode on a surface of said substrate, and

a piezoelectric film configured to cover said surface of said substrate and a surface of said interdigital electrode, wherein:

said substrate is a langasite single crystal belonging to a point group 32, and when a cut angle of said substrate cut out of the langasite single crystal and a propagation direction of surface acoustic waves on said substrate are represented in terms of Euler angles (.phi., .theta., .psi.), where

-5.degree..ltoreq..phi..ltoreq.5.degree.

85.degree..ltoreq..theta..ltoreq.95.degree.

10.degree..ltoreq..psi.<25.degree., and

said piezoelectric film is a c-axis oriented ZnO film that satisfies:

0<h/.lambda..ltoreq.0.4

where h is a thickness of said ZnO film, and .lambda. is a wavelength of a surface acoustic wave.

7. A surface acoustic wave device comprising:

a substrate,

an interdigital electrode on a surface of said substrate, and

a piezoelectric film configured to cover said surface of said substrate and a surface of said interdigital electrode, wherein:

said substrate is a langasite single crystal belonging to a point group 32, and when a cut angle of said substrate cut out of the langasite single crystal and a propagation direction of surface acoustic waves on said substrate are represented in terms of Euler angles (.phi., .theta., .psi.), where

-.degree..ltoreq..phi..ltoreq. .degree.

85.degree..ltoreq..theta..ltoreq.95.degree.

25.degree..ltoreq..psi.<35.degree., and

said piezoelectric film is a c-axis oriented ZnO film that satisfies:

0<h/.lambda..ltoreq.0.45

where h is a thickness of said ZnO film, and .lambda. is a wavelength of a surface acoustic wave.

8. A surface acoustic wave device comprising:

a substrate,

an interdigital electrode on a surface of said substrate, and

a piezoelectric film configured to cover said surface of said substrate and a surface of said interdigital electrode, wherein:

said substrate is a langasite single crystal belonging to a point group 32, and when a cut angle of said substrate cut out of the langasite single crystal and a propagation direction of surface acoustic waves on said substrate are represented in terms of Euler angles (.phi., .theta., .psi.), where

-5.degree..ltoreq..phi..ltoreq.5.degree.

85.degree..ltoreq..theta..ltoreq.95.degree.

35.degree..ltoreq..psi.<50.degree., and

said piezoelectric film is a c-axis oriented ZnO film that satisfies:

0<h/.lambda..ltoreq.0.4

where h is a thickness of said ZnO film, and .lambda. is a wavelength of a surface acoustic wave.

9. A surface acoustic wave device comprising:

a substrate,

an interdigital electrode on a surface of said substrate, and

a piezoelectric film configured to cover said surface of said substrate and a surface of said interdigital electrode, wherein:

said substrate is a langasite single crystal belonging to a point group 32, and when a cut angle of said substrate cut out of the langasite single crystal and a propagation direction of surface acoustic waves on said substrate are represented in terms of Euler angles (.phi., .theta., .psi.), where

-50.degree..ltoreq..phi..ltoreq.5.degree.

85.degree..ltoreq..theta..ltoreq.95.degree.

50.degree..ltoreq..psi.<70.degree., and

said piezoelectric film is a c-axis oriented ZnO film that satisfies:

h/.lambda.=0.15 to 0.7

where h is a thickness of said ZnO film, and .lambda. is a wavelength of a surface acoustic wave.

10. A surface acoustic wave device comprising:

a substrate,

an interdigital electrode on a surface of said substrate, and

a piezoelectric film configured to cover said surface of said substrate and a surface of said interdigital electrode, wherein:

said substrate is a langasite single crystal belonging to a point group 32, and when a cut angle of said substrate cut out of the langasite single crystal and a propagation direction of surface acoustic waves on said substrate are represented in terms of Euler angles (.phi., .theta., .psi.), where

-5.degree..ltoreq..phi..ltoreq.5.degree.

85.degree..ltoreq..theta..ltoreq.95.degree.

70.degree..ltoreq..psi.<90.degree., and

said piezoelectric film is a c-axis oriented ZnO film that satisfies:

h/.lambda.=0.15 to 0.18

where h is a thickness of said ZnO film, and .lambda. is a wavelength of a surface acoustic wave.

11. A surface acoustic wave device comprising:

a substrate,

a piezoelectric film on a surface of said substrate, and

an interdigital electrode on a surface of said piezoelectric film, wherein:

said substrate is a langasite single crystal belonging to a point group 32, and when a cut angle of said substrate cut out of the langasite single crystal and a propagation direction of surface acoustic waves on said substrate are represented in terms of Euler angles (.phi., .theta., .psi.), where

-.degree..ltoreq..phi..ltoreq. .degree.

85.degree..ltoreq..theta..ltoreq.95.degree.

-90.degree..ltoreq..psi.<-70.degree., and

said piezoelectric film is a c-axis oriented ZnO film that satisfies:

h/.lambda.=0.05 to 0.8

where h is a thickness of said ZnO film, and .lambda. is a wavelength of a surface acoustic wave.

12. A surface acoustic wave device comprising:

a substrate,

a piezoelectric film on a surface of said substrate, and

an interdigital electrode on a surface of said piezoelectric film, wherein:

said substrate is a langasite single crystal belonging to a point group 32, and when a cut angle of said substrate cut out of the langasite single crystal and a propagation direction of surface acoustic waves on said substrate are represented in terms of Euler angles (.phi., .theta., .psi.), where

-5.degree..ltoreq..phi..ltoreq.5.degree.

85.degree..ltoreq..theta..ltoreq.95.degree.

-70.degree..ltoreq..psi.<-50.degree., and

said piezoelectric film is a c-axis oriented ZnO film that satisfies:

h/.lambda.=0.05 to 0.75

where h is a thickness of said ZnO film, and .lambda. is a wavelength of a surface acoustic wave.

13. A surface acoustic wave device comprising:

a substrate,

a piezoelectric film on a surface of said substrate, and

an interdigital electrode on a surface of said piezoelectric film, wherein:

said substrate is a langasite single crystal belonging to a point group 32, and when a cut angle of said substrate cut out of the langasite single crystal and a propagation direction of surface acoustic waves on said substrate are represented in terms of Euler angles (.phi., .theta., .psi.), where

-5.degree..ltoreq..phi..ltoreq.5.degree.

85.degree..ltoreq..theta..ltoreq.95.degree.

-50.degree..ltoreq..psi.<-35.degree., and

said piezoelectric film is a c-axis oriented ZnO film that satisfies:

0<h/.lambda..ltoreq.0.45

where h is a thickness of said ZnO film, and .lambda. is a wavelength of a surface acoustic wave.

14. A surface acoustic wave device comprising:

a substrate,

a piezoelectric film on a surface of said substrate, and

an interdigital electrode on a surface of said piezoelectric film, wherein:

said substrate is a langasite single crystal belonging to a point group 32, and when a cut angle of said substrate cut out of the langasite single crystal and a propagation direction of surface acoustic waves on said substrate are represented in terms of Euler angles (.phi., .theta., .psi.) where

-.degree..ltoreq..phi..ltoreq. .degree.

85.degree..ltoreq..theta..ltoreq.95.degree.

-35.degree..ltoreq..psi.<-35.degree., and

said piezoelectric film is a c-axis oriented ZnO film that satisfies:

0<h/.lambda..ltoreq.0.5

where h is a thickness of said ZnO film, and .lambda. is wavelength of a surface acoustic wave.

15. A surface acoustic wave device comprising:

a substrate,

a piezoelectric film on a surface of said substrate, and

an interdigital electrode on a surface of said piezoelectric film, wherein:

said substrate is a langasite single crystal belonging to a point group 32, and when a cut angle of said substrate cut out of the langasite single crystal and a propagation direction of surface acoustic waves on said substrate are represented in terms of Euler angles (.phi., .theta., .psi.), where

-5.degree..ltoreq..phi..ltoreq.5.degree.

85.degree..ltoreq..theta..ltoreq.95.degree.

-25.degree..ltoreq..psi.<-10.degree., and

said piezoelectric film is a c-axis oriented ZnO film that satisfies:

0<h/.lambda..ltoreq.0.45

where h is a thickness of said ZnO film, and .lambda. is a wavelength of a surface acoustic wave.

16. A surface acoustic wave device comprising:

a substrate,

a piezoelectric film on a surface of said substrate, and

an interdigital electrode on a surface of said piezoelectric film, wherein:

said substrate is a langasite single crystal belonging to a point group 32, and when a cut angle of said substrate cut out of the langasite single crystal and a propagation direction of surface acoustic waves on said substrate are represented in terms of Euler angles (.phi., .theta., .psi.), where

-5.degree..ltoreq..phi..ltoreq.5.degree.

85.degree..ltoreq..theta..ltoreq.95.degree.

10.degree..ltoreq..psi.<25.degree., and

said piezoelectric film is a c-axis oriented ZnO film that satisfies:

0<h/.lambda..ltoreq.0.4

where h is a thickness of said ZnO film, and .lambda. is a wavelength of a surface acoustic wave.

17. A surface acoustic wave device comprising:

a substrate,

a piezoelectric film on a surface of said substrate, and

an interdigital electrode on a surface of said piezoelectric film, wherein:

said substrate is a langasite single crystal belonging to a point group 32, and when a cut angle of said substrate cut out of the langasite single crystal and a propagation direction of surface acoustic waves on said substrate are represented in terms of Euler angles (.phi., .theta., .psi.), where

-.degree..ltoreq..phi..ltoreq. .degree.

85.degree..ltoreq..theta..ltoreq.95.degree.

25.degree..ltoreq..psi.<35.degree., and

said piezoelectric film is a c-axis oriented ZnO film that satisfies:

0<h/.lambda..ltoreq.0.45

where h is a thickness of said ZnO film, and .lambda. is a wavelength of a surface acoustic wave.

18. A surface acoustic wave device comprising:

a substrate,

a piezoelectric film on a surface of said substrate, and

an interdigital electrode on a surface of said piezoelectric film, wherein:

said substrate is a langasite single crystal belonging to a point group 32, and when a cut angle of said substrate cut out of the langasite single crystal and a propagation direction of surface acoustic waves on said substrate are represented in terms of Euler angles (.phi., .theta., .psi.), where

-5.degree..ltoreq..phi..ltoreq.5.degree.

85.degree..ltoreq..theta..ltoreq.95.degree.

35.degree..ltoreq..psi.<35.degree., and

said piezoelectric film is a c-axis oriented ZnO film that satisfies:

0<h/.lambda..ltoreq.0.4

where h is a thickness of said ZnO film, and .lambda. is a wavelength of a surface acoustic wave.

19. A surface acoustic wave device comprising:

a substrate,

a piezoelectric film on a surface of said substrate, and

an interdigital electrode on a surface of said piezoelectric film, wherein:

said substrate is a langasite single crystal belonging to a point group 32, and when a cut angle of said substrate cut out of the langasite single crystal and a propagation direction of surface acoustic waves on said substrate are represented in terms of Euler angles (.phi., .theta., .psi.), where

-5.degree..ltoreq..phi..ltoreq.5.degree.

85.degree..ltoreq..theta..ltoreq.95.degree.

50.degree..ltoreq..psi.<70.degree., and

said piezoelectric film is a c-axis oriented ZnO film that satisfies:

h/.lambda.=0.05 to 0.7

where h is a thickness of said ZnO film, and .lambda. is a wavelength of a surface acoustic wave.

20. A surface acoustic wave device comprising:

a substrate,

a piezoelectric film on a surface of said substrate, and

an interdigital electrode on a surface of said piezoelectric film, wherein:

said substrate is a langasite single crystal belonging to a point group 32, and when a cut angle of said substrate cut out of the langasite single crystal and a propagation direction of surface acoustic waves on said substrate are represented in terms of Euler angles (.phi., .theta., .psi.), where

-.degree..ltoreq..phi..ltoreq. .degree.

85.degree..ltoreq..theta..ltoreq.95.degree.

70.degree..ltoreq..psi.<90.degree., and

said piezoelectric film is a c-axis oriented ZnO film that satisfies:

h/.lambda.=0.05 to 0.8

where h is a thickness of said ZnO film, and .lambda. is wavelength of a surface acoustic wave.

21. A surface acoustic wave device comprising:

a substrate,

an interdigital electrode on a surface of said substrate, and

a piezoelectric film configured to cover said surface of said substrate and a surface of said interdigital electrode and an opposite electrode film on a surface of said piezoelectric film, wherein:

said substrate is a langasite single crystal belonging to a point group 32, and when a cut angle of said substrate cut out of the langasite single crystal and a propagation direction of surface acoustic waves on said substrate are represented in terms of Euler angles (.phi., .theta., .psi.), where

-5.degree..ltoreq..phi..ltoreq.5.degree.

85.degree..ltoreq..theta..ltoreq.95.degree.

-90.degree..ltoreq..psi.<-70.degree., and

said piezoelectric film is a c-axis oriented ZnO film that satisfies:

0<h/.lambda..ltoreq.0.1 or 0.3.ltoreq.h/.lambda..ltoreq.0.8

where h is a thickness of said ZnO film, and .lambda. is a wavelength of a surface acoustic wave.

22. A surface acoustic wave device comprising:

a substrate,

an interdigital electrode on a surface of said substrate, and

a piezoelectric film configured to cover said surface of said substrate and a surface of said interdigital electrode and an opposite electrode film on a surface of said piezoelectric film, wherein:

said substrate is a langasite single crystal belonging to a point group 32, and when a cut angle of said substrate cut out of the langasite single crystal and a propagation direction of surface acoustic waves on said substrate are represented in terms of Euler angles (.phi., .theta., .psi.), where

-5.degree..ltoreq..phi..ltoreq.5.degree.

85.degree..ltoreq..theta..ltoreq.95.degree.

-70.degree..ltoreq..psi.<-50.degree., and

said piezoelectric film is a c-axis oriented ZnO film that satisfies:

0<h/.lambda..ltoreq.0.1 or 0.35.ltoreq.h/.lambda..ltoreq.0.8

where h is a thickness of said ZnO film, and .psi. is wavelength of a surface acoustic wave.

23. A surface acoustic wave device comprising

a substrate,

an interdigital electrode on a surface of said substrate, and

a piezoelectric film configured to cover said surface of said substrate and a surface of said interdigital electrode and an opposite electrode film on a surface of said piezoelectric film, wherein:

said substrate is a langasite single crystal belonging to a point group 32, and when a cut angle of said substrate cut out of the langasite single crystal and a propagation direction of surface acoustic waves on said substrate are represented in terms of Euler angles (.phi., .theta., .psi.), where

-5.degree..ltoreq..phi..ltoreq.5.degree.

85.degree..ltoreq..theta..ltoreq.95.degree.

-50.degree..ltoreq..psi.<-35.degree., and

said piezoelectric film is a c-axis oriented ZnO film that satisfies:

0<h/.lambda..ltoreq.0.15 or 0.35.ltoreq.h/.lambda..ltoreq.0.5

where h is a thickness of said ZnO film, and .lambda. is a wavelength of a surface acoustic wave.

24. A surface acoustic wave device comprising:

a substrate,

an interdigital electrode on a surface of said substrate, and

a piezoelectric film configured to cover said surface of said substrate and a surface of said interdigital electrode and an opposite electrode film on a surface of said piezoelectric film, wherein:

said substrate is a langasite single crystal belonging to a point group 32, and when a cut angle of said substrate cut out of the langasite single crystal and a propagation direction of surface acoustic waves on said substrate are represented in terms of Euler angles (.phi., .theta., .psi.), where

-.degree..ltoreq..phi..ltoreq. .degree.

85.degree..ltoreq..theta..ltoreq.95.degree.

-35.degree..ltoreq..psi.<-25.degree., and

said piezoelectric film is a c-axis oriented ZnO film that satisfies:

0<h/.lambda..ltoreq.0.15 or 0.3.ltoreq.h/.lambda..ltoreq.0.5

where h is a thickness of said ZnO film, and .lambda. is a wavelength of a surface acoustic wave.

25. A surface acoustic wave device comprising:

a substrate,

an interdigital electrode on a surface of said substrate, and

a piezoelectric film configured to cover said surface of said substrate and a surface of said interdigital electrode and an opposite electrode film on a surface of said piezoelectric film, wherein:

said substrate is a langasite single crystal belonging to a point group 32, and when a cut angle of said substrate cut out of the langasite single crystal and a propagation direction of surface acoustic waves on said substrate are represented in terms of Euler angles (.phi., .theta., .psi.), where

-5.degree..ltoreq..phi..ltoreq.5.degree.

85.degree..ltoreq..theta..ltoreq.95.degree.

-25.degree..ltoreq..psi..ltoreq.-10.degree., and

said piezoelectric film is a c-axis oriented ZnO film that satisfies:

0<h/.lambda..ltoreq.0.15 or 0.3.ltoreq.h/.lambda..ltoreq.0.45

where h is a thickness of said ZnO film, and .lambda. is a wavelength of a surface acoustic wave.

26. A surface acoustic wave device comprising:

a substrate,

an interdigital electrode on a surface of said substrate, and

a piezoelectric film configured to cover said surface of said substrate and a surface of said interdigital electrode and an opposite electrode film on a surface of said piezoelectric film, wherein:

said substrate is a langasite single crystal belonging to a point group 32, and when a cut angle of said substrate cut out of the langasite single crystal and a propagation direction of surface acoustic waves on said substrate are represented in terms of Euler angles (.phi., .theta., .psi.) where

-5.degree..ltoreq..phi..ltoreq.5.degree.

85.degree..ltoreq..theta..ltoreq.95.degree.

10.degree..ltoreq..psi.<25.degree., and

said piezoelectric film is a c-axis oriented ZnO film that satisfies:

0<h/.lambda..ltoreq.0.45

where h is a thickness of said ZnO film, and .lambda. is a wavelength of a surface acoustic wave.

27. A surface acoustic wave device comprising:

a substrate,

an interdigital electrode on a surface of said substrate, and

a piezoelectric film configured to cover said surface of said substrate and a surface of said interdigital electrode and an opposite electrode film on a surface of said piezoelectric film, wherein:

said substrate is a langasite single crystal belonging to a point group 32, and when a cut angle of said substrate cut out of the langasite single crystal and a propagation direction of surface acoustic waves on said substrate are represented in terms of Euler angles (.phi., .theta., .psi.), where

-5.degree..ltoreq..phi..ltoreq.5.degree.

85.degree..ltoreq..theta..ltoreq.95.degree.

25.degree..ltoreq..psi.<35.degree., and

said piezoelectric film is a c-axis oriented ZnO film that satisfies:

0<h/.lambda..ltoreq.0.5

where h is a thickness of said ZnO film, and .lambda. is a wavelength of a surface acoustic wave.

28. A surface acoustic wave device comprising:

a substrate,

an interdigital electrode on a surface of said substrate, and

a piezoelectric film configured to cover said surface of said substrate and a surface of said interdigital electrode and an opposite electrode film on a surface of said piezoelectric film, wherein:

said substrate is a langasite single crystal belonging to a point group 32, and when a cut angle of said substrate cut out of the langasite single crystal and a propagation direction of surface acoustic waves on said substrate are represented in terms of Euler angles (.phi., .theta., .psi.), where

-.degree..ltoreq..phi..ltoreq. .degree.

85.degree..ltoreq..theta..ltoreq.95.degree.

35.degree..ltoreq..psi.<50.degree., and

said piezoelectric film is a c-axis oriented ZnO film that satisfies:

0<h/.lambda..ltoreq.0.45

where h is a thickness of said ZnO film, and .lambda. is a wavelength of a surface acoustic wave.

29. A surface acoustic wave device comprising:

a substrate,

an interdigital electrode on a surface of said substrate, and

a piezoelectric film configured to cover said surface of said substrate and a surface of said interdigital electrode and an opposite electrode film on a surface of said piezoelectric film, wherein:

said substrate is a langasite single crystal belonging to a point group 32, and when a cut angle of said substrate cut out of the langasite single crystal and a propagation direction of surface acoustic waves on said substrate are represented in terms of Euler angles (.phi., .theta., .psi.), where

-5.degree..ltoreq..phi..ltoreq.5.degree.

85.degree..ltoreq..theta..ltoreq.95.degree.

50.degree..ltoreq..psi.<70.degree., and

said piezoelectric film is a c-axis oriented ZnO film that satisfies:

0<h/.lambda..ltoreq.0.05 or 0.2<h/.lambda..ltoreq.0.8

where h is a thickness of said ZnO film, and .lambda. is a wavelength of a surface acoustic wave.

30. A surface acoustic wave device comprising:

a substrate,

an interdigital electrode on a surface of said substrate, and

a piezoelectric film configured to cover said surface of said substrate and a surface of said interdigital electrode and an opposite electrode film on a surface of said piezoelectric film, wherein:

said substrate is a langasite single crystal belonging to a point group 32, and when a cut:angle of said substrate cut out of the langasite single crystal and a propagation direction of surface acoustic waves on said substrate are represented in terms of Euler angles (.phi., .theta., .psi.), where

-5.degree..ltoreq..phi..ltoreq.5.degree.

85.degree..ltoreq..theta..ltoreq.95.degree.

70.degree..ltoreq..psi.<90.degree., and

said piezoelectric film is a c-axis oriented ZnO film that satisfies:

0<h/.lambda..ltoreq.0.5 or 0.25.ltoreq.h/.lambda..ltoreq.0.8

where h is a thickness of said ZnO film, and .lambda. is a wavelength of a surface acoustic wave.

31. A surface acoustic wave device comprising:

a substrate,

an opposite electrode film on a surface of said substrate, and

a piezoelectric film on said opposite electrode film and an interdigital electrode on a surface of said piezoelectric film, wherein:

said substrate is a langasite single crystal belonging to a point group 32, and when a cut angle of said substrate cut out of the langasite single crystal and a propagation direction of surface acoustic waves on said substrate are represented in terms of Euler angles (.phi., .theta., .psi.), where

-5.degree..ltoreq..phi..ltoreq.5.degree.

85.degree..ltoreq..theta..ltoreq.95.degree.

-90.degree..ltoreq..psi.<-70.degree., and

said piezoelectric film is a c-axis oriented ZnO film that satisfies:

h/.lambda.=0.05 to 0.8

where h is a thickness of said ZnO film, and .lambda. is a wavelength of a surface acoustic wave.

32. A surface acoustic wave device comprising:

a substrate,

an opposite electrode film on a surface of said substrate, and

a piezoelectric film on said opposite electrode film and an interdigital electrode on a surface of said piezoelectric film, wherein:

said substrate is a langasite single crystal belonging to a point group 32, and when a cut angle of said substrate cut out of the langasite single crystal and a propagation direction of surface acoustic waves on said substrate are represented in terms of Euler angles (.phi., .theta., .psi.), where

-.degree..ltoreq..phi..ltoreq. .degree.

85.degree..ltoreq..theta..ltoreq.95.degree.

-70.degree..ltoreq..psi.<-50.degree., and

said piezoelectric film is a c-axis oriented ZnO film that satisfies:

h/.lambda.=0.05 to 0.8

where h is a thickness of said ZnO film, and .lambda. is a wavelength of a surface acoustic wave.

33. A surface acoustic wave device comprising:

a substrate,

an opposite electrode film on a surface of said substrate, and

a piezoelectric film on said opposite electrode film and an interdigital electrode on a surface of said piezoelectric film, wherein:

said substrate is a langasite single crystal belonging to a point group 32, and when a cut angle of said substrate cut out of the langasite single crystal and a propagation direction of surface acoustic waves on said substrate are represented in terms of Euler angles (.phi., .theta., .psi.), where

-5.degree..ltoreq..phi..ltoreq.5.degree.

85.degree..ltoreq..theta..ltoreq.95.degree.

-50.degree..ltoreq..psi.<-35.degree., and

said piezoelectric film is a c-axis oriented ZnO film that satisfies:

h/.lambda.=0.05 to 0.45

where h is a thickness of said ZnO film, and .lambda. is a wavelength of a surface acoustic wave.

34. A surface acoustic wave device comprising:

a substrate,

an opposite electrode film on a surface of said substrate, and

a piezoelectric film on said opposite electrode film and an interdigital electrode on a surface of said piezoelectric film, wherein:

said substrate is a langasite single crystal belonging to a point group 32, and when a cut angle of said substrate cut out of the langasite single crystal and a propagation direction of surface acoustic waves on said substrate are represented in terms of Euler angles (.phi., .theta., .psi.), where

-5.degree..ltoreq..phi..ltoreq.5.degree.

85.degree..ltoreq..theta..ltoreq.95.degree.

-35.degree..ltoreq..psi.<-25.degree., and

said piezoelectric film is a c-axis oriented ZnO film that satisfies:

h/.lambda.=0.05 to 0.5

where h is a thickness of said ZnO film, and .lambda. is a wavelength of a surface acoustic wave.

35. A surface acoustic wave device comprising:

a substrate,

an opposite electrode film on a surface of said substrate, and

a piezoelectric film on said opposite electrode film and an interdigital electrode on a surface of said piezoelectric film, wherein:

said substrate is a langasite single crystal belonging to a point group 32, and when a cut angle of said substrate cut out of the langasite single crystal and a propagation direction of surface acoustic waves on said substrate are represented in terms of Euler angles (.phi., .theta., .psi.), where

-5.degree..ltoreq..phi..ltoreq.5.degree.

85.degree..ltoreq..theta..ltoreq.95.degree.

-25.degree..ltoreq..psi.<-10.degree., and

said piezoelectric film is a c-axis oriented ZnO film that satisfies:

h/.lambda.=0.05 to 0.45

where h is a thickness of said ZnO film, and .lambda. is a wavelength of a surface acoustic wave.

36. A surface acoustic wave device comprising:

a substrate,

an opposite electrode film on a surface of said substrate, and

a piezoelectric film on said opposite electrode film and an interdigital electrode on a surface of said piezoelectric film, wherein:

said substrate is a langasite single crystal belonging to a point group 32, and when a cut angle of said substrate cut out of the langasite single crystal and a propagation direction of surface acoustic waves on said substrate are represented in terms of Euler angles (.phi., .theta., where

-.degree..ltoreq..phi..ltoreq. .degree.

85.degree..ltoreq..theta..ltoreq.95.degree.

10.degree..ltoreq..psi.<25.degree., and

said piezoelectric film is a c-axis oriented ZnO film that satisfies:

h/.lambda.=0.05 to 0.45

where h is a thickness of said ZnO film, and .lambda. is a wavelength of a surface acoustic wave.

37. A surface acoustic wave device comprising:

a substrate,

an opposite electrode film on a surface of said substrate, and

a piezoelectric film on said opposite electrode film and an interdigital electrode on a surface of said piezoelectric film, wherein:

said substrate is a langasite single crystal belonging to a point group 32, and when a cut angle of said substrate cut out of the langasite single crystal and a propagation direction of surface acoustic waves on said substrate are represented in terms of Euler angles (.phi., .theta., where

-5.degree..ltoreq..phi..ltoreq.5.degree.

85.degree..ltoreq..theta..ltoreq.95.degree.

25.degree..ltoreq..psi.<35.degree., and

said piezoelectric film is a c-axis oriented ZnO film that satisfies:

h/.lambda.=0.05 to 0.5

where h is a thickness of said ZnO film, and .lambda. is a wavelength of a surface acoustic wave.

38. A surface acoustic wave device comprising:

a substrate,

an opposite electrode film on a surface of said substrate, and

a piezoelectric film on said opposite electrode film and a n interdigital electrode on a surface of said piezoelectric film, where in:

said substrate is a langasite single crystal belonging to a point group 32, and when a cut angle of said substrate cut out of the langasite single crystal and a propagation direction of surface acoustic waves on said substrate are represented in terms of Euler angles (.phi., .theta., .psi.), where

-5.degree..ltoreq..phi..ltoreq.5.degree.

85.degree..ltoreq..theta..ltoreq.95.degree.

35.degree..ltoreq..psi.<50.degree., and

said piezoelectric film is a c-axis oriented ZnO film that satisfies:

h/.lambda.=0.05 to 0.45

where h is a thickness of said ZnO film, and .lambda. is a wavelength of a surface acoustic wave.

39. A surface acoustic wave device comprising:

a substrate,

an opposite electrode film on a surface of said substrate, and

a piezoelectric film on said opposite electrode film and an interdigital electrode on a surface of said piezoelectric film, wherein:

said substrate is a langasite single crystal belonging to a point group 32, and when a cut angle of said substrate cut out of the langasite single crystal and a propagation direction of surface acoustic waves on said substrate are represented in terms of Euler angles (.phi., .theta., .psi.), where

-.degree..ltoreq..phi..ltoreq. .degree.

85.degree..ltoreq..theta..ltoreq.95.degree.

50.degree..ltoreq..psi.<70.degree., and

said piezoelectric film is a c-axis oriented ZnO film that satisfies:

h/.lambda.=0.05 to 0.8

where h is a thickness of said ZnO film, and .lambda. is a wavelength of a surface acoustic wave.

40. A surface acoustic wave device comprising:

a substrate,

an opposite electrode film on a surface of said substrate, and

a piezoelectric film on said opposite electrode film and an interdigital electrode on a surface of said piezoelectric film, wherein:

said substrate is a langasite single crystal belonging to a point group 32, and when a cut angle of said substrate cut out of the langasite single crystal and a propagation direction of surface acoustic waves on said substrate are represented in terms of Euler angles (.phi., .theta., .psi.), where

-5.degree..ltoreq..phi..ltoreq.5.degree.

85.degree..ltoreq..theta..ltoreq.95.degree.

70.degree..ltoreq..psi.<90.degree., and

said piezoelectric film is a c-axis oriented ZnO film that satisfies:

h/.lambda.=0.05 to 0.8

where h is a thickness of said ZnO film, and .lambda. is a wavelength of a surface acoustic wave.