Surface acoustic wave device, electronic component using the device, and composite module

1. A surface acoustic wave device comprising:

a piezoelectric substrate; and

an electrode including

a first metal layer provided on said piezoelectric substrate and having a trapezoid shape in a cross section, and

a second metal layer provided over said piezoelectric substrate at a same position as said first metal layer,

wherein said piezoelectric substrate is etched to a depth not greater than 10 nm at a portion where said electrode is not formed thereon.

2. The surface acoustic wave device according to claim 1 , wherein said first metal layer and said second metal layer are different from each other in etching rate.

3. The surface acoustic wave device according to claim 2 , wherein said first metal layer has an etching rate greater than said second metal layer.

4. The surface acoustic wave device according to claim 2 , wherein said etching rate is based on a dry etching process.

5. The surface acoustic wave device according to claim 1 , wherein said first metal layer and said second metal layer are different from each other in re-aggregation after vaporization.

6. The surface acoustic wave device according to claim 1 , wherein said first metal layer contains Al, and said second metal layer contains one of Ti and Ta.

7. The surface acoustic wave device according to claim 1 , wherein said second metal layer is located between said first metal layer and said piezoelectric substrate.

8. The surface acoustic wave device according to claim 1 , wherein said second metal layer is located on said first metal layer.

9. The surface acoustic wave device according to claim 8 , wherein said second metal layer is an uppermost layer of said electrode.

10. The surface acoustic wave device according to claim 1 , wherein a side surface of said second metal layer has an undulation smaller than a side surface of said first metal layer.

11. The surface acoustic wave device according to claim 1 , wherein said electrode has a side surface thereof arranged substantially smooth.

12. The surface acoustic wave device according to claim 1 , wherein a side surface of said electrode has an undulation not greater than 5 nm.

13. The surface acoustic wave device according to claim 1 , wherein an inclination angle of a side surface of said electrode ranges from 70 to 80 degrees.

14. The surface acoustic wave device according to claim 1 , wherein an interlayer difference between respective side surfaces of said first metal layer and said second metal layer is not greater than 5 nm.

15. The surface acoustic wave device according to claim 1 , further comprising

another electrode provided on said piezoelectric substrate,

wherein a width (L) of a lowermost of said electrode is L and a distance (S) between said electrode and said another electrode satisfy that L/(L+S) ranges from 0.58 to 0.65.

16. The surface acoustic wave device according to claim 1 , wherein a width (A) of an uppermost of said electrode farthest from said piezoelectric substrate and a width (L) of a lowermost of said electrode closest to said piezoelectric substrate satisfy that A/L ranges from 0.8 to 0.9.

17. The surface acoustic wave device according to claim 1 , wherein a width (A) of an uppermost of said electrode farthest from said piezoelectric substrate and a width (L) of a lowermost of said electrode closest to said piezoelectric substrate satisfy that A/L ranges from 1.1 to 1.3.

18. The surface acoustic wave device according to claim 1 , wherein a shape of a cross section of said electrode is symmetrical from left to right.

19. The surface acoustic wave device according to claim 1 , further comprising

a protective layer for covering at least said electrode.

20. The surface acoustic wave device according to claim 19 , wherein said protective layer has an insulating property.

21. A surface acoustic wave device comprising:

a piezoelectric substrate; and

an electrode including

a first metal layer provided over said piezoelectric substrate and having a cross section of a rectangular shape, and

a second metal layer provided over said first metal layer and being wider than said first metal layer,

wherein a side surface of said second metal layer has an undulation smaller than a side surface of said first metal layer.

22. The surface acoustic wave device according to claim 21 , wherein a width (A) of an uppermost of said electrode and a width (L) of a lowermost of said electrode satisfy that A/L ranges from 0.98 to 1.01.

23. A surface acoustic wave device comprising:

a piezoelectric substrate; and

an electrode including

a first metal layer provided over said piezoelectric substrate and having a cross section of a rectangular shape, and

second metal layer provided over said first metal layer and being wider than said first metal layer,

wherein said piezoelectric substrate has a portion etched to a depth not greater than 10 nm where said electrode is not formed thereon.

24. The surface acoustic wave device according to claim 23 , wherein said first metal layer and said second metal layer are different from each other in etching rate.

25. The surface acoustic wave device according to claim 24 , wherein said first metal layer has an etching rate greater than said second metal layer.

26. The surface acoustic wave device according to claim 24 , wherein said etching rate is based on an dry etching process.

27. The surface acoustic wave device according to claim 23 , wherein said first metal layer and said second metal layer are different from each other in re-aggregation after vaporization.

28. The surface acoustic wave device according to claim 23 , wherein said first metal layer contains Al, and said second metal layer contains one of Ti and Ta.

29. The surface acoustic wave device according to claim 23 , further comprising

another electrode provided on said piezoelectric substrate,

wherein a width (L) of a lowermost of said electrode and a distance (S) between said electrodes and said another electrode satisfy that L/(L+S) ranges from 0.58 to 0.65.

30. The surface acoustic wave device according to claim 23 , further comprising

a protective layer for covering at least said electrode.

31. The surface acoustic wave device according to claim 30 , wherein said protective layer has an insulating property.

32. A surface acoustic wave device comprising:

a piezoelectric substrate; and

an electrode including

a first metal layer provided over said piezoelectric substrate and having a cross section of a rectangular shape, and

a second metal layer provided over said first metal layer and being wider than said first metal layer,

wherein a side surface of said electrode has an undulation not greater than 5 nm.

33. A surface acoustic wave device comprising:

a piezoelectric substrate; and

an electrode including

a first metal layer provided over said piezoelectric substrate and having a cross section of a rectangular shape, and

a second metal layer provided over said first metal layer and being wider than said first metal layer,

wherein a interlayer difference between respective side surfaces of said first metal layer and said second metal layer is not greater than 5 nm.

34. A surface acoustic wave device comprising:

a piezoelectric substrate; and

an electrode including

a first metal layer provided over said piezoelectric substrate and having a cross section of a rectangular shape, and

a second metal layer provided over said first metal layer and being wider than said first metal layer,

wherein a width (A) of an uppermost of said electrode distanced farthest from said piezoelectric substrate and a width (L) of a lowermost of said electrode closest to said piezoelectric substrate satisfy that A/L ranges from 0.98 to 1.01.

35. A surface acoustic wave device comprising:

a piezoelectric substrate

an electrode provided on said piezoelectric substrate and having a projection provided on a side surface thereof, said electrode including

a first metal layer, and

a second metal layer provided on said first metal layer;

a protective layer for covering at least an upper surface and said side surface of said electrode; and

a third metal layer provided between said first metal layer and said piezoelectric substrate.

36. The surface acoustic wave device according to claim 35 , wherein said third metal layer is a lowermost layer of said electrode and contains one of Ti and Ta.

37. A surface acoustic wave device comprising:

a piezoelectric substrate;

an electrode including

a first metal layer provided on said piezoelectric substrate and having a trapezoid shape in a cross section, and

a second metal layer provided over said piezoelectric substrate at a same position as said first metal layer; and

another electrode provided on said piezoelectric substrate,

wherein a width (L) of a lowermost of said electrode is L and a distance (S) between said electrode and said another electrode satisfy that L/(L+S) ranges from 0.58 to 0.65.

38. A surface acoustic wave device comprising:

a piezoelectric substrate; and

an electrode including

a first metal layer provided on said piezoelectric substrate and having a trapezoid shape in a cross section, and

a second metal layer provided over said piezoelectric substrate at a same position as said first metal layer,

wherein a width (A) of an uppermost of said electrode farthest from said piezoelectric substrate and a width (L) of a lowermost of said electrode closest to said piezoelectric substrate satisfy that A/L ranges from 1.1 to 1.3.

39. A surface acoustic wave device comprising:

a piezoelectric substrate;

an electrode provided on said piezoelectric substrate and having a projection provided on a side surface thereof, said electrode including

a first metal layer, and

a second metal layer provided on said first metal layer; and

a protective layer for covering at least an upper surface and said side surface of said electrode,

wherein a cross section of said first metal layer has a trapezoid shape.

40. The surface acoustic wave device according to claim 39 , wherein said first metal layer and said second metal layer are different from each other in etching rate.

41. The surface acoustic wave device according to claim 40 , wherein said first metal layer has an etching rate greater than said second metal layer.

42. The surface acoustic wave device according to claim 39 , wherein a side surface of said second metal layer extends outwardly of a side surface of said first metal layer so as to form said projection.

43. The surface acoustic wave device according to claim 39 , wherein said first metal layer contains Al.

44. The surface acoustic wave device according to claim 39 , wherein said second metal layer contains one of Ti and Ta.

45. The surface acoustic wave device according to claim 39 , wherein said second metal layer is an uppermost layer of said electrode.

46. The surface acoustic wave device according to claim 39 , wherein a cross section of said second metal layer has a rectangular shape.

47. The surface acoustic wave device according to claim 39 , wherein said protective layer has an insulating property.

48. The surface acoustic wave device according to claim 47 , wherein said protective layer is made of material selected from a group consisting of silicon oxide, silicon nitride, silicon carbide, aluminum oxide, aluminum nitride, and magnesium oxide.

49. A surface acoustic wave device comprising:

a piezoelectric substrate; and

an electrode including

a first metal layer provided on said piezoelectric substrate and having a trapezoid shape in a cross section, and

a second metal layer provided over said piezoelectric substrate at a same position as said first metal layer,

wherein a side surface of said second metal layer has an undulation smaller than a side surface of said first metal layer.

50. A surface acoustic wave device comprising:

a piezoelectric substrate; and

an electrode including

a first metal layer provided on said piezoelectric substrate and having a trapezoid shape in a cross section, and

a second metal layer provided over said piezoelectric substrate at a same position as said first metal layer

wherein a side surface of said electrode has an undulation not greater than 5 nm.

51. A surface acoustic wave device comprising:

a piezoelectric substrate; and

an electrode including

a first metal layer provided on said piezoelectric substrate and having a trapezoid shape in a cross section, and

a second metal layer provided over said piezoelectric substrate at a same position as said first metal layer,

wherein an interlayer difference between respective side surfaces of said first metal layer and said second metal layer is not greater than 5 nm.

52. An electronic apparatus comprising:

said surface acoustic wave device according to claim 1 , 32 , or 45 ;

a mounting member for accommodating said surface acoustic wave device; and

a connector provided at said surface acoustic wave device for electrically connecting said surface acoustic wave device with said mounting member.

53. The electronic apparatus according to claim 52 , wherein said connector includes a bump provided on said surface acoustic wave device.

54. The electronic apparatus according to claim 52 , wherein said connector includes a wire provided between said surface acoustic wave device and said mounting member.

55. The electronic apparatus according to claim 52 , wherein said mounting member is a platform or a package.

56. A composite module comprising:

said surface acoustic wave device according to claim 1 , 32 , or 45 ;

a circuit connected to said surface acoustic wave device; and

a mounting member having said circuit therein and having said surface acoustic wave device mounted thereto.

57. The composite module according to claim 56 , wherein said mounting member is a platform.