Temperature compensated acoustic resonator device having an interlayer

1. An acoustic resonator device comprising:

a composite first electrode disposed over a substrate, the composite first electrode comprising: a first electrically conductive layer provided over the substrate; a first interlayer disposed on the first electrically conductive layer; a buried temperature compensation layer disposed over the first interlayer; a second interlayer disposed over the temperature compensation layer, and a second electrically conductive layer disposed over the second interlayer;

a piezoelectric layer disposed over the composite first electrode, the piezoelectric layer having a negative temperature coefficient; and

a second electrode disposed over the piezoelectric layer.

2. An acoustic resonator device as claimed in claim 1 , wherein the piezoelectric layer has a negative temperature coefficient and at least one of the first electrically conductive layer, the second electrically conductive layer and the second electrode has a positive temperature coefficient that offsets at least a portion of the negative temperature coefficient of the piezoelectric layer.

3. An acoustic resonator device as claimed in claim 1 , wherein at least one of the first and second interlayers has a positive temperature coefficient.

4. An acoustic resonator as claimed in claim 1 , wherein the second interlayer comprises a seed layer that fosters growth of highly textured piezoelectric material.

5. An acoustic resonator device as claimed in claim 1 , wherein the first interlayer is an etch-stop layer.

6. An acoustic resonator as claimed in claim 1 , wherein the first interlayer comprises a same material as the piezoelectric layer.

7. An acoustic resonator as claimed in claim 6 , wherein the material comprises aluminum nitride (AlN).

8. An acoustic resonator as claimed in claim 1 , wherein the second interlayer comprises a same material as the piezoelectric layer, or a material having a hexagonal crystal structure, or composition of interlayer from same piezoelectric layer (AlN) and hexagonal crystal structure materials.

9. An acoustic resonator as claimed in claim 8 , wherein the piezoelectric layer comprises aluminum nitride (AlN).

10. An acoustic resonator as claimed in claim 8 , wherein the material has a thickness in the range of approximately 10 1 Å to approximately 10 3 Å.

11. An acoustic resonator as claimed in claim 8 , wherein the material has a thickness in the range of approximately 60 Å to approximately 150 Å.

12. An acoustic resonator device as claimed in claim 5 , wherein the first interlayer comprises one of: Aluminum (Al), Silicon Carbide (SiC), Titanium Tungsten (TiW), or titanium oxynitride (TiO x N y ).

13. An acoustic resonator device comprising:

a composite first electrode disposed over a substrate, the composite first electrode comprising: a first electrically conductive layer provided over the substrate; an interlayer disposed on the first electrical conductive layer; a buried temperature compensation layer disposed over the interlayer; and a second electrically conductive layer disposed over the buried temperature compensation layer;

a piezoelectric layer disposed over the composite first electrode; and

a second electrode disposed over the piezoelectric layer.

14. An acoustic resonator device as claimed in claim 13 , wherein the piezoelectric layer has a negative temperature coefficient and at least one of the first electrically conductive layer, the second electrically conductive layer and the second electrode has a positive temperature coefficient that offsets at least a portion of the negative temperature coefficient of the piezoelectric layer.

15. An acoustic resonator device as claimed in claim 13 , wherein the interlayer has a positive temperature coefficient.

16. An acoustic resonator as claimed in claim 13 , wherein the interlayer comprises a same material as the piezoelectric layer.

17. An acoustic resonator as claimed in claim 13 , wherein the material comprises aluminum nitride (AlN).

18. An acoustic resonator as claimed in claim 16 , wherein the material has a thickness in the range of approximately 10 1 Å to approximately 10 3 Å.

19. An acoustic resonator comprising:

a first electrode disposed over a substrate;

a piezoelectric layer disposed over the first electrode; and

a composite second electrode comprising disposed over the piezoelectric layer, the second electrode comprising: a first electrically conductive layer provided over the piezoelectric layer; a second electrically conductive layer disposed over the first electrically conductive layer; a buried temperature compensating layer provided between the first and second electrically conductive layers; and an interlayer disposed beneath the buried temperature compensating layer and over the first electrically conductive layer.

20. An acoustic resonator as claimed in claim 19 , wherein the piezoelectric layer has a negative temperature coefficient and at least one of the first electrically conductive layer, the second electrically conductive layer and the second electrode has a positive temperature coefficient that offsets at least a portion of the negative temperature coefficient of the piezoelectric layer.

21. An acoustic resonator as claimed in claim 19 , wherein the interlayer is an etch-stop layer.

22. An acoustic resonator as claimed in claim 21 , wherein the interlayer comprises one of: Aluminum Nitride (AlN), Aluminum (Al), Silicon Carbide (SiC), Titanium Tungsten (TiW), or titanium oxynitride (TiO x N y ).