Acoustic wave device, high frequency front end circuit, and communication apparatus
An acoustic wave device includes a material layer which has Euler angles and an elastic constant at the Euler angles, a piezoelectric body which includes first and second principal surfaces opposing each other, is laminated directly or indirectly on the material layer so that the second principal surface is on the material layer side and has Euler angles, and whose elastic constant at the Euler angles, and an IDT electrode which is disposed on at least one of the first principal surface and the second principal surface of the piezoelectric body. At least one elastic constant among elastic constants C 11 to C 66 of the material layer not equal to 0 and at least one elastic constant among elastic constants C 11 to C 66 of the piezoelectric body not equal to 0 have opposite signs to each other.
1. An acoustic wave device comprising:
a material layer with Euler angles (φ 1 , θ 1 , ψ 1 ) and an elastic constant at the Euler angles (φ 1 , θ 1 , ψ 1 ) that is represented by:
(
C
11
C
12
C
13
C
14
C
15
C
16
C
21
C
22
C
23
C
24
C
25
C
26
C
31
C
32
C
33
C
34
C
35
C
36
C
41
C
42
C
43
C
44
C
45
C
46
C
51
C
52
C
53
C
54
C
55
C
56
C
61
C
62
C
63
C
64
C
65
C
66
)
;
Expression
1
a piezoelectric body that includes first and second principal surfaces opposing each other, is laminated directly or indirectly on the material layer so that the second principal surface on a material layer side and has Euler angles (φ 2 , θ 2 , ψ 2 ), and has an elastic constant at the Euler angles (φ 2 , θ 2 , ψ 2 ) that is represented by Expression 1; and
an IDT electrode disposed on at least one of the first principal surface and the second principal surface of the piezoelectric body; wherein
at least one elastic constant among elastic constants C 11 to C 66 of the material layer not equal to 0 and at least one elastic constant among elastic constants C 11 to C 66 of the piezoelectric body not equal to 0 at a symmetrical position relative to the at least one elastic constant of the material layer have opposite signs to each other.
2. The acoustic wave device according to claim 1 , further comprising a low acoustic velocity film which is disposed between the material layer and the piezoelectric body, and in which a bulk wave propagates at a lower acoustic velocity than an acoustic velocity of an acoustic wave propagating in the piezoelectric body.
3. The acoustic wave device according to claim 2 , further comprising a high acoustic velocity film which is laminated between the low acoustic velocity film and the material layer, and in which a bulk wave propagates at a higher acoustic velocity than the acoustic velocity of the acoustic wave propagating in the piezoelectric body.
4. The acoustic wave device according to claim 3 , wherein the high acoustic velocity film is a silicon nitride film.
5. The acoustic wave device according to claim 4 , wherein a film thickness of the silicon nitride film is equal to or greater than about 0.25λ and equal to or smaller than about 0.55λ.
6. The acoustic wave device according to claim 2 , wherein the low acoustic velocity film is a silicon oxide film.
7. The acoustic wave device according to claim 6 , wherein the low acoustic velocity film has a thickness of equal to or smaller than about 2λ.
8. The acoustic wave device according to claim 1 , wherein the elastic constants having the opposite signs of the material layer and the piezoelectric body are at least one of C 41 to C 43 , C 51 to C 54 , C 61 to C 65 , C 14 , C 24 , C 34 , C 15 , C 25 , C 35 , C 45 , C 16 , C 26 , C 36 , C 46 , and C 56 in Expression 1.
9. The acoustic wave device according to claim 8 , wherein the elastic constants having the opposite signs of the material layer and the piezoelectric body include the elastic constant C 41 or C 14 in Expression 1.
10. The acoustic wave device according to claim 8 , wherein the elastic constants having the opposite signs of the material layer and the piezoelectric body include the elastic constant C 42 or C 24 in Expression 1.
11. The acoustic wave device according to claim 8 , wherein the elastic constants having the opposite signs of the material layer and the piezoelectric body include the elastic constant C 56 or C 65 in Expression 1.
12. The acoustic wave device according to claim 1 , wherein
when an elastic constant of the material layer before a rotating operation is defined as c ab 0 , the elastic constant c ab at the Euler angles (φ 1 , θ 1 , ψ 1 ) is determined by an equation of (c ab )=[α] −1 [c ab 0 ] [β], and when an elastic constant of the piezoelectric body before a rotating operation is defined as c ab 1 , the elastic constant c ab of the piezoelectric body at the Euler angles (φ 2 , θ 2 , ψ 2 ) is determined by an equation of (c ab )=[α] −1 [c ab 1 ] [β], and α and β are:
α
=
(
l
1
2
l
2
2
l
3
2
2
l
2
l
3
2
l
3
l
1
2
l
1
l
2
m
1
2
m
2
2
m
3
2
2
m
2
m
3
2
m
3
m
1
2
m
1
m
2
n
1
2
n
2
2
n
3
2
2
n
2
n
3
2
n
3
n
1
2
n
1
n
2
m
1
n
1
m
2
n
2
m
3
n
3
m
2
n
3
+
m
3
n
2
m
3
n
1
+
m
1
n
3
m
1
n
2
+
m
2
n
1
n
1
l
1
n
2
l
2
n
3
l
3
n
2
l
3
+
n
3
l
2
n
3
l
1
+
n
1
l
3
n
1
l
2
+
n
2
l
1
l
1
m
1
l
2
m
2
l
3
m
3
l
2
m
3
+
l
3
m
2
l
3
m
1
+
l
1
m
3
l
1
m
2
+
l
2
m
1
)
β
=
(
l
1
2
l
2
2
l
3
2
l
2
l
3
l
3
l
1
l
1
l
2
m
1
2
m
2
2
m
3
2
m
2
m
3
m
3
m
1
m
1
m
2
n
1
2
n
2
2
n
3
2
n
2
n
3
n
3
n
1
n
1
n
2
2
m
1
n
1
2
m
2
n
2
2
m
3
n
3
m
2
n
3
+
m
3
n
2
m
3
n
1
+
m
1
n
3
m
1
n
2
+
m
2
n
1
2
n
1
l
1
2
n
2
l
2
2
n
3
l
3
n
2
l
3
+
n
3
l
2
n
3
l
1
+
n
1
l
3
n
1
l
2
+
n
2
l
1
2
l
1
m
1
2
l
2
m
2
2
l
3
m
3
l
2
m
3
+
l
3
m
2
l
3
m
1
+
l
1
m
3
l
1
m
2
+
l
2
m
1
)
;
where l 1 , l 2 , l 3 , m 1 , m 2 , m 3 , n 1 , n 2 , and n 3 are:
l 1 =cos ψ cos φ−cos θ sin φ sin ψ
l 2 =−sin ψ cos φ−cos θ sin φ cos ψ
l 3 =sin θ sin φ
m 1 =cos ψ sin φ+cos θ cos φ sin ψ
m 2 =−sin ψ sin φ+cos θ cos φ cos ψ
m 3 =−sin θ cos φ
n 1 =sin ψ sin θ
n 2 =cos ψ sin θ
n 3 =cos θ.
13. The acoustic wave device according to claim 1 , wherein at least a portion of a high-order mode excited by the IDT electrode propagates through both of the material layer and the piezoelectric body.
14. The acoustic wave device according to claim 1 , wherein an absolute value of the elastic constant of the material layer having the opposite sign is equal to or greater than about 1 GPa.
15. The acoustic wave device according to claim 1 , wherein the material layer is made of a high acoustic velocity material in which a bulk wave propagates at a higher acoustic velocity than an acoustic velocity of an acoustic wave propagating in the piezoelectric body.
16. The acoustic wave device according to claim 1 , wherein the material layer is made of a material other than a piezoelectric body.
17. The acoustic wave device according to claim 1 , wherein the material layer is made of a single crystal.
18. The acoustic wave device according to claim 1 , wherein the piezoelectric body is made of a single crystal.
19. The acoustic wave device according to claim 1 , wherein the piezoelectric body has a thickness of equal to or smaller than about 10λ.
20. The acoustic wave device according to claim 1 , wherein the material layer is made of silicon.