Acoustic wave device, filter, and multiplexer
An acoustic wave device includes a support substrate, a piezoelectric layer provided on the support substrate, at least one pair of comb-shaped electrodes provided on the piezoelectric layer, the at least one pair of comb-shaped electrodes including a plurality of electrode fingers, a first intermediate layer provided between the support substrate and the piezoelectric layer, a second intermediate layer provided between the support substrate and the first intermediate layer, the second intermediate layer having a porosity higher than a porosity of the first intermediate layer, and a third intermediate layer provided between the support substrate and the second intermediate layer, the third intermediate layer having a porosity lower than the porosity of the second intermediate layer.
1 . An acoustic wave device comprising:
a support substrate;
a piezoelectric layer provided on the support substrate;
at least one pair of comb-shaped electrodes provided on the piezoelectric layer, the at least one pair of comb-shaped electrodes including a plurality of electrode fingers;
a first intermediate layer provided between the support substrate and the piezoelectric layer;
a second intermediate layer provided between the support substrate and the first intermediate layer, the second intermediate layer having a porosity higher than a porosity of the first intermediate layer; and
a third intermediate layer provided between the support substrate and the second intermediate layer, the third intermediate layer having a porosity lower than the porosity of the second intermediate layer.
2 . The acoustic wave device according to claim 1 ,
wherein the first intermediate layer has a porosity of 3% or less,
wherein the second intermediate layer has a porosity of 5% or greater, and
wherein a porosity of the third intermediate layer is 3% or less.
3 . The acoustic wave device according to claim 1 , wherein the second intermediate layer and the third intermediate layer are made of the same material.
4 . The acoustic wave device according to claim 1 , wherein the third intermediate layer has a thickness of 15 nm or greater and 1500 nm or less.
5 . The acoustic wave device according to claim 1 , wherein the third intermediate layer is provided between the second intermediate layer and the first intermediate layer and on a side surface of the second intermediate layer.
6 . The acoustic wave device according to claim 1 , wherein the first intermediate layer includes: a fourth intermediate layer that is a silicon oxide film; and a fifth intermediate layer that is provided between the silicon oxide film and the second intermediate layer and is an aluminum oxide film, an aluminum nitride film, an aluminum oxynitride film, a silicon nitride film, or a silicon carbide film.
7 . The acoustic wave device according to claim 6 , wherein the piezoelectric layer is a monocrystalline lithium tantalate substrate or a monocrystalline lithium niobate substrate.
8 . The acoustic wave device according to claim 1 , wherein a thickness of the piezoelectric layer is equal to or less than two times an average pitch of the plurality of electrode fingers.
9 . A filter comprising the acoustic wave device according to claim 1 .
10 . A multiplexer comprising the filter according to claim 9 .
11 . An acoustic wave device comprising:
a support substrate;
a piezoelectric layer provided on the support substrate;
at least one pair of comb-shaped electrodes provided on the piezoelectric layer, the at least one pair of comb-shaped electrodes including a plurality of electrode fingers;
a first intermediate layer provided between the support substrate and the piezoelectric layer;
a second intermediate layer provided between the support substrate and the first intermediate layer, the second intermediate layer having a Q factor smaller than a Q factor of the first intermediate layer; and
a third intermediate layer provided between the support substrate and the second intermediate layer, the third intermediate layer having a Q factor larger than the Q factor of the second intermediate layer.
12 . The acoustic wave device according to claim 11 , wherein the second intermediate layer and the third intermediate layer are made of the same material.
13 . The acoustic wave device according to claim 11 , wherein the third intermediate layer has a thickness of 15 nm or greater and 1500 nm or less.
14 . The acoustic wave device according to claim 11 , wherein the third intermediate layer is provided between the second intermediate layer and the first intermediate layer and on a side surface of the second intermediate layer.
15 . The acoustic wave device according to claim 11 , wherein the first intermediate layer includes: a fourth intermediate layer that is a silicon oxide film; and a fifth intermediate layer that is provided between the silicon oxide film and the second intermediate layer and is an aluminum oxide film, an aluminum nitride film, an aluminum oxynitride film, a silicon nitride film, or a silicon carbide film.
16 . The acoustic wave device according to claim 15 , wherein the piezoelectric layer is a monocrystalline lithium tantalate substrate or a monocrystalline lithium niobate substrate.
17 . The acoustic wave device according to claim 11 , wherein a thickness of the piezoelectric layer is equal to or less than two times an average pitch of the plurality of electrode fingers.
18 . A filter comprising the acoustic wave device according to claim 11 .
19 . A multiplexer comprising the filter according to claim 18 .