Acoustic wave device
An acoustic wave device is provided that includes a piezoelectric layer and first and second resonators. The first resonator includes a first functional electrode and a first dielectric film on the piezoelectric layer. The second resonator includes a second functional electrode and a second dielectric film on the piezoelectric layer. The piezoelectric layer includes first and second resonator portions respectively including portions of the first and second resonators. Moreover, a resonant frequency of the first resonator is lower than that of the second resonator. A thickness of the first resonator portion is greater than that of the second resonator portion, and ts 1 /tp 1 ≤ts 2 /tp 2 is satisfied, where tp 1 , tp 2 , ts 1 , and ts 2 are respectively thicknesses of the first and second resonator portions and the first and second dielectric films.
1. An acoustic wave device comprising:
a first resonator including:
a piezoelectric substrate including a piezoelectric layer;
a first functional electrode on the piezoelectric layer; and
a first dielectric film on the piezoelectric layer and covering the first functional electrode; and
a second resonator that includes the piezoelectric layer, the second resonator including:
a second functional electrode on the piezoelectric layer; and
a second dielectric film on the piezoelectric layer and covering the second functional electrode,
wherein the piezoelectric layer includes a first resonator portion and a second resonator portion, a portion of the first resonator being in the first resonator portion, a portion of the second resonator being in the second resonator portion;
wherein a resonant frequency of the first resonator is lower than a resonant frequency of the second resonator and, in the piezoelectric layer, a thickness of the first resonator portion is greater than a thickness of the second resonator portion, and
wherein ts 1 /tp 1 ≤ts 2 /tp 2 , where tp 1 is the thickness of the first resonator portion, tp 2 is the thickness of the second resonator portion, ts 1 is a thickness of the first dielectric film, and tp 2 is a thickness of the second dielectric film.
2. The acoustic wave device according to claim 1 , wherein the first resonator and the second resonator are configured to use a thickness resonance mode.
3. The acoustic wave device according to claim 1 , wherein ts 1 /tp 1 =ts 2 /tp 2 .
4. The acoustic wave device according to claim 1 , wherein the first dielectric film of the first resonator and the second dielectric film of the second resonator comprise a same dielectric material.
5. The acoustic wave device according to claim 1 , wherein the first dielectric film of the first resonator and the second dielectric film of the second resonator comprise different dielectric materials.
6. The acoustic wave device according to claim 1 , wherein the piezoelectric layer comprises lithium tantalate or lithium niobate.
7. The acoustic wave device according to claim 6 , wherein the first resonator and the second resonator are configured to use bulk waves in a thickness-shear mode that is a thickness resonance mode.
8. The acoustic wave device according to claim 7 , wherein:
Euler angles (φ, θ, ψ) of the piezoelectric layer are within one of the ranges represented by the following expressions (1), (2), and (3):
(0°±10°, 0° to 20°, ψ of any value) (1);
(0°±10°, 20° to 80°, 0° to 60°(1−(θ−50) 2 /900) 1/2 ) or (0°±10°, 20° to 80°, [180°−60° (1−(θ−50) 2 /900) 1/2 ] to 180°) (2); and
(0°±10°, [180°−30°(1−(ψ−90) 2 /8100) 1/2 ] to 180°, ψ of any value) (3).
9. The acoustic wave device according to claim 6 , wherein:
each of the first functional electrode and the second functional electrode includes at least one pair of electrodes, and
the piezoelectric substrate includes a support and the piezoelectric layer on the support.
10. The acoustic wave device according to claim 9 , further comprising a first acoustic reflector and a second acoustic reflector disposed in the support, with the first acoustic reflector overlapping at least a portion of the first functional electrode in a plan view, and the second acoustic reflector overlapping at least a portion of the second functional electrode in the plan view.
11. The acoustic wave device according to claim 10 , wherein the first resonator and the second resonator each satisfy a condition where d/p is less than or equal to 0.5, where d represents a thickness of the piezoelectric layer and p represents a distance between centers of adjacent electrodes of the at least one pair of electrodes, respectively.
12. The acoustic wave device according to claim 11 , wherein d/p is less than or equal to about 0.24.
13. The acoustic wave device according to claim 11 , wherein, in each of the first functional electrode and the second functional electrode, an excitation region is a region where the adjacent electrodes overlap each other in a direction in which the adjacent electrodes face-to-face.
14. The acoustic wave device according to claim 13 , wherein MR≤1.75(d/p)+0.075, where MR is a metallization ratio of the at least one pair of the electrodes to the excitation region.
15. The acoustic wave device according to claim 10 , wherein each of the first acoustic reflector and the second acoustic reflector is a cavity.
16. The acoustic wave device according to claim 10 , wherein each of the first acoustic reflector and the second acoustic reflector are at least one Bragg reflector.
17. An acoustic wave device comprising:
a first resonator including at least one piezoelectric layer, a first electrode on the at least one piezoelectric layer, and a first dielectric film on the at least one piezoelectric layer and the first electrode; and
a second resonator including the at least one piezoelectric layer, a second electrode on the at least one piezoelectric layer, and a second dielectric film on the at least one piezoelectric layer and the second electrode,
wherein the at least one piezoelectric layer includes a first resonator portion tp 1 that includes the first resonator and a second resonator portion tp 2 that includes the second resonator,
wherein a thickness of the first resonator portion tp 1 is greater than a thickness of the second resonator portion tp 2 , and
wherein ts 1 /tp 1 ≤ts 2 /tp 2 , where ts 1 is a thickness of the first dielectric film, and tp 2 is a thickness of the second dielectric film.
18. The acoustic wave device according to claim 17 ,
wherein a resonant frequency of the first resonator is lower than a resonant frequency of the second resonator,
wherein the first resonator and the second resonator are configured to use a thickness resonance mode.
19. The acoustic wave device according to claim 17 , wherein:
each of the first electrode and the second electrode includes at least one pair of electrodes, and
wherein the first resonator and the second resonator each satisfy a condition where d/p is less than or equal to about 0.5, where d represents a thickness of the at least one piezoelectric layer and p represents a distance between centers of adjacent electrodes of the at least one pair of electrodes, respectively.
20. The acoustic wave device according to claim 19 , wherein d/p is less than or equal to about 0.24.