Acoustic wave device
An acoustic wave device includes an IDT electrode on a piezoelectric substrate and reflector electrodes on both sides of the IDT electrode in an acoustic wave propagation direction and each including electrode fingers with gaps therebetween, and first dielectric films between the reflector electrodes and the piezoelectric substrate in regions where the electrode fingers and the gaps of the reflector electrodes are provided.
1 . An acoustic wave device comprising:
a piezoelectric substrate;
an interdigital transducer (IDT) electrode on the piezoelectric substrate;
reflector electrodes on both sides of the IDT electrode in an acoustic wave propagation direction and including a plurality of electrode fingers with gaps therebetween; and
a first dielectric film between the reflector electrodes and the piezoelectric substrate in regions where the plurality of electrode fingers and the gaps of the reflector electrodes are provided; wherein
the first dielectric film is not provided between at least a portion of the IDT electrode and the piezoelectric substrate.
2 . The acoustic wave device according to claim 1 , wherein
the IDT electrode includes a plurality of first electrode fingers and a plurality of second electrode fingers that interdigitate with each other;
a region where the first electrode fingers and the second electrode fingers overlap in the acoustic wave propagation direction is a crossing region;
the crossing region includes a center region and first and second edge regions on both sides of the center region in a direction in which the first and second electrode fingers extend; and
a second dielectric film is provided between the IDT electrode and the piezoelectric substrate in the first and second edge regions.
3 . The acoustic wave device according to claim 1 , wherein the first dielectric film is made of tantalum oxide, niobium oxide, tungsten oxide, hafnium oxide, or cerium oxide.
4 . The acoustic wave device according to claim 1 , wherein the piezoelectric substrate is made of a piezoelectric material including LiNbO 3 or LiTaO 3 .
5 . The acoustic wave device according to claim 1 , wherein
the piezoelectric substrate includes a support substrate and a piezoelectric film directly or indirectly stacked on the support substrate; and
the piezoelectric film is made of LiNbO 3 or LiTaO 3 .
6 . The acoustic wave device according to claim 5 , wherein the piezoelectric substrate further includes a high acoustic velocity material layer between the piezoelectric film and the support substrate and made of a high acoustic velocity material in which an acoustic velocity of a bulk wave propagating therein is higher than an acoustic velocity of an acoustic wave propagating in the piezoelectric film.
7 . The acoustic wave device according to claim 6 , further comprising a low acoustic velocity film between the high acoustic velocity material layer and the piezoelectric film, and made of a low acoustic velocity material in which an acoustic velocity of a bulk wave propagating therein is lower than an acoustic velocity of a bulk wave propagating in the piezoelectric film.
8 . The acoustic wave device according to claim 6 , wherein the high acoustic velocity material layer is integrated with the support substrate.
9 . The acoustic wave device according to claim 5 , wherein the piezoelectric substrate further includes an acoustic reflective film between the piezoelectric film and the support substrate.
10 . The acoustic wave device according to claim 9 , wherein the acoustic reflective film includes a low acoustic impedance layer having a relatively low acoustic impedance and a high acoustic impedance layer having a relatively high acoustic impedance.
11 . An acoustic wave device comprising:
a piezoelectric substrate;
an interdigital transducer (IDT) electrode on the piezoelectric substrate;
reflector electrodes on both sides of the IDT electrode in an acoustic wave propagation direction and including a plurality of electrode fingers with gaps therebetween; and
a first dielectric film between the plurality of electrode fingers of the reflector electrodes and the piezoelectric substrate and not provided in any portion of a region between the piezoelectric substrate and regions where the gaps of the reflector electrodes are provided.
12 . The acoustic wave device according to claim 11 , wherein
the IDT electrode includes a plurality of first electrode fingers and a plurality of second electrode fingers that interdigitate with each other;
a region where the first electrode fingers and the second electrode fingers overlap in the acoustic wave propagation direction is a crossing region;
the crossing region includes a center region and first and second edge regions on both sides of the center region in a direction in which the first and second electrode fingers extend; and
a second dielectric film is provided between the IDT electrode and the piezoelectric substrate in the first and second edge regions.
13 . The acoustic wave device according to claim 11 , wherein the first dielectric film is made of tantalum oxide, niobium oxide, tungsten oxide, hafnium oxide, or cerium oxide.
14 . The acoustic wave device according to claim 11 , wherein the piezoelectric substrate is made of a piezoelectric material including LiNbO 3 or LiTaO 3 .
15 . The acoustic wave device according to claim 11 , wherein
the piezoelectric substrate includes a support substrate and a piezoelectric film directly or indirectly stacked on the support substrate; and
the piezoelectric film is made of LiNbO 3 or LiTaO 3 .
16 . The acoustic wave device according to claim 15 , wherein the piezoelectric substrate further includes a high acoustic velocity material layer between the piezoelectric film and the support substrate and made of a high acoustic velocity material in which an acoustic velocity of a bulk wave propagating therein is higher than an acoustic velocity of an acoustic wave propagating in the piezoelectric film.
17 . The acoustic wave device according to claim 16 , further comprising a low acoustic velocity film between the high acoustic velocity material layer and the piezoelectric film, and made of a low acoustic velocity material in which an acoustic velocity of a bulk wave propagating therein is lower than an acoustic velocity of a bulk wave propagating in the piezoelectric film.
18 . The acoustic wave device according to claim 16 , wherein the high acoustic velocity material layer is integrated with the support substrate.
19 . The acoustic wave device according to claim 15 , wherein the piezoelectric substrate further includes an acoustic reflective film between the piezoelectric film and the support substrate.
20 . The acoustic wave device according to claim 19 , wherein the acoustic reflective film includes a low acoustic impedance layer having a relatively low acoustic impedance and a high acoustic impedance layer having a relatively high acoustic impedance.