Guided surface acoustic wave device providing spurious mode rejection

1. A Surface Acoustic Wave (SAW) device, comprising:

a non-semiconductor support substrate;

a piezoelectric layer on a surface of the non-semiconductor support substrate; and

at least one Interdigitated Transducer (IDT) on a surface of the piezoelectric layer opposite the non-semiconductor support substrate, wherein a thickness of the piezoelectric layer, a SAW velocity of the piezoelectric layer, and an acoustic velocity of the non-semiconductor support substrate are such that a frequency of spurious modes above a resonance frequency of the SAW device is above a bulk wave cut-off frequency of the SAW device such that the spurious modes are suppressed.

2. The SAW device of claim 1 wherein the piezoelectric layer comprises Lithium Tantalate.

3. The SAW device of claim 1 wherein the piezoelectric layer comprises Lithium Niobate.

4. The SAW device of claim 1 wherein the thickness of the piezoelectric layer is less than two times λ, where λ is a wavelength of the resonance frequency of the SAW device, and the bulk wave cut-off frequency is greater than fa+(fa−fr) /2, where fr is the resonance frequency of the SAW device and fa is an anti-resonance frequency of the SAW device.

5. The SAW device of claim 4 wherein a velocity of a slowest acoustic mode in a propagation direction of the non-semiconductor support substrate is less than 6,984 meters per second.

6. The SAW device of claim 4 wherein a velocity of a slowest acoustic mode in a propagation direction of the non-semiconductor support substrate is less than 6,000 meters per second.

7. The SAW device of claim 4 wherein a velocity of a slowest acoustic mode in a propagation direction of the non-semiconductor support substrate is less than 5,400 meters per second.

8. The SAW device of claim 1 wherein the thickness of the piezoelectric layer is less than two times λ, where λ is a wavelength of the resonance frequency of the SAW device, and a velocity of a slowest acoustic mode in a propagation direction of the non-semiconductor support substrate is between 1.07 times a surface wave velocity in the at least one IDT and 6,984 meters per second.

9. The SAW device of claim 1 wherein the thickness of the piezoelectric layer is less than two times λ, where λ is a wavelength of the resonance frequency of the SAW device, and a velocity of a slowest acoustic mode in a propagation direction of the non-semiconductor support substrate is between 1.07 times a surface wave velocity in the at least one IDT and 6,000 meters per second.

10. The SAW device of claim 1 wherein the thickness of the piezoelectric layer is less than two times λ, where λ is a wavelength of the resonance frequency of the SAW device, and a velocity of a slowest acoustic mode in a propagation direction of the non-semiconductor support substrate is between 1.07 times a surface wave velocity in the at least one IDT and 5,400 meters per second.

11. The SAW device of claim 1 wherein the thickness of the piezoelectric layer is less than a defined maximum thickness of the piezoelectric layer that supports spurious mode suppression, the defined maximum thickness of the piezoelectric layer being a function of both the SAW velocity of the piezoelectric layer and a velocity of a slowest acoustic mode in a propagation direction of the non-semiconductor support substrate.

12. The SAW device of claim 11 wherein:

there are no dielectric layers between the non-semiconductor support substrate and the piezoelectric layer; and

the defined maximum thickness of the piezoelectric layer is, in units of λ, 1.76−2.52×10 −4 ×(V sub +4210−V piezo ), where V sub is a velocity of a slowest acoustic mode in a propagation direction of the non-semiconductor support substrate and V piezo is the SAW velocity of the piezoelectric layer in units of meters per second.

13. The SAW device of claim 12 wherein the thickness of the piezoelectric layer is greater than 0.05 times λ, where λ is a wavelength of the resonance frequency of the SAW device, and a velocity of a slowest acoustic mode in a propagation direction of the non-semiconductor support substrate is less than 6,984 meters per second.

14. The SAW device of claim 12 wherein the thickness of the piezoelectric layer is greater than 0.1 times λ, where λ is a wavelength of the resonance frequency of the SAW device, and a velocity of a slowest acoustic mode in a propagation direction of the non-semiconductor support substrate is less than 6,984 meters per second.

15. The SAW device of claim 12 wherein a velocity of a slowest acoustic mode in a propagation direction of the non-semiconductor support substrate is less than 6,000 meters per second.

16. The SAW device of claim 12 wherein a velocity of a slowest acoustic mode in a propagation direction of the non-semiconductor support substrate is less than 5,400 meters per second.

17. The SAW device of claim 11 wherein:

there are no dielectric layers between the non-semiconductor support substrate and the piezoelectric layer;

the piezoelectric layer comprises rotated Y-cut, X propagation Lithium Tantalate (LT); and

the defined maximum thickness of the piezoelectric layer is, in units of λ, 1.76−2.52×10 −4 ×(V sub +4210−(−2.435×10 −9 θ 6 +1.103×10 −6 θ 5 −1.719×10 −4 θ 4 +1.145×10 −2 θ 3 −4.229×10 −1 θ 2 +9.765θ+4.103×10 3 )), where V sub is a velocity of a slowest acoustic mode in a propagation direction of the non-semiconductor support substrate in units of meters per second and θ is a cut-angle of the rotated Y-cut LT in units of degree.

18. The SAW device of claim 11 further comprising a Silicon Oxide dielectric layer between the non-semiconductor support substrate and the piezoelectric layer, wherein:

the defined maximum thickness of the piezoelectric layer is, in units of λ, 1.76−2.52×10 −4 ×(V sub +4210−V piezo )−0.50×T SiO2 , where V sub is a velocity of a slowest acoustic mode in a propagation direction of the non-semiconductor support substrate in units of meters per second and V piezo is the SAW velocity of the piezoelectric substrate in units of meters per second and T SiO2 is the thickness of the Silicon Oxide dielectric layer in units of wavelength λ.

19. The SAW device of claim 18 wherein the thickness of the piezoelectric layer is greater than 0.05 times λ, where λ is a wavelength of the resonance frequency of the SAW device, and a velocity of a slowest acoustic mode in a propagation direction of the non-semiconductor support substrate is less than 6,984 meters per second.

20. The SAW device of claim 18 wherein the thickness of the piezoelectric layer is greater than 0.1 times λ, where λ is a wavelength of the resonance frequency of the SAW device, and a velocity of a slowest acoustic mode in a propagation direction of the non-semiconductor support substrate is less than 6,984 meters per second.

21. The SAW device of claim 18 wherein a velocity of a slowest acoustic mode in a propagation direction of the non-semiconductor support substrate is less than 6,000 meters per second.

22. The SAW device of claim 18 wherein a velocity of a slowest acoustic mode in a propagation direction of the non-semiconductor support substrate is less than 5,400 meters per second.

23. The SAW device of claim 11 further comprising a Silicon Oxide dielectric layer between the non-semiconductor support substrate and the piezoelectric layer, wherein:

the piezoelectric layer comprises rotated Y-cut, X propagation Lithium Tantalate (LT); and

the defined maximum thickness of the piezoelectric layer is, in units of λ, 1.76−2.52×10 −4 ×{V sub +4210−(−2.435×10 −9 θ 6 +1.103×10 −6 θ 5 −1.719×10 −4 θ 4 +1.145×10 −2 θ 3 −4.229×10 −1 θ 2 +9.765θ+4.103×10 3 )}−0.50×T SiO2 , where V sub is a velocity of a slowest acoustic mode in a propagation direction of the non-semiconductor support substrate in units of meters per second, θ is a cut-angle of the rotated Y-cut LT in units of degree, and T SiO2 is a thickness of the Silicon Oxide dielectric layer in units of wavelength λ.

24. The SAW device of claim 11 further comprising a Silicon Oxide dielectric layer between the non-semiconductor support substrate and the piezoelectric layer, wherein a thickness of the Silicon Oxide dielectric layer is less than 0.1 times λ, where λ is a wavelength of the resonance frequency of the SAW device.

25. The SAW device of claim 1 wherein the piezoelectric layer is single crystal.

26. The SAW device of claim 1 wherein the non-semiconductor substrate is made from a water.