Acoustic wave device
An acoustic wave device includes a piezoelectric film directly or indirectly provided on a high acoustic-velocity material layer, a dielectric film on the piezoelectric film, and an IDT electrode on the dielectric film. The dielectric film is made of one of silicon oxide, silicon nitride, alumina, and amorphous silicon. When a wavelength determined based on an electrode finger pitch of the IDT electrode is denoted as λ, a duty of the IDT electrode is denoted as y, and a film thickness normalized by the wavelength λ of the dielectric film is denoted as x (%), x and y are in each range of Table 1, Table 2, Table 3, or Table 4 below depending on a material of the dielectric film.
1 . An acoustic wave device comprising:
a high acoustic-velocity material layer made of a high acoustic-velocity material;
a piezoelectric film directly or indirectly provided on the high acoustic-velocity material layer; and
an IDT electrode on the piezoelectric film; wherein
the high acoustic-velocity material is a material in which an acoustic velocity of a bulk wave propagating therethrough is higher than an acoustic velocity of an acoustic wave propagating through the piezoelectric film;
the acoustic wave device further includes a dielectric film between the IDT electrode and the piezoelectric film; and
the dielectric film is made of one of silicon oxide, silicon nitride, alumina, and amorphous silicon, and when a wavelength determined based on an electrode finger pitch of the IDT electrode is denoted as λ, a duty of the IDT electrode is denoted as y, and a film thickness normalized by the wavelength λ of the dielectric film is denoted as x (%), the film thickness x of the dielectric film and the duty y of the IDT electrode are in a range of Table 1 below in a structure in which the dielectric film is made of silicon oxide, the film thickness x and the duty y are in a range of Table 2 below in a structure in which the dielectric film is made of silicon nitride, the film thickness x and the duty y are in a range of Table 3 below in a structure in which the dielectric film is made of alumina, and the film thickness x and the duty y are in a range of Table 4 below in a structure in which the dielectric film is made of amorphous silicon:
TABLE 1
When 0.2 ≤ x < 0.3, 0.5 < y ≤ 0.51
When 0.3 ≤ x < 0.4, 0.5 < y ≤ 0.54
When 0.4 ≤ x < 0.5, 0.5 < y ≤ 0.58
When 0.5 ≤ x < 0.6, 0.5 < y ≤ 0.61
When 0.6 ≤ x < 0.7, 0.5 < y ≤ 0.64
When 0.7 ≤ x < 0.8, 0.5 < y ≤ 0.66
When 0.8 ≤ x < 0.9, 0.5 < y ≤ 0.67
When 0.9 ≤ x < 1.0, 0.5 < y ≤ 0.69
When 1.0 ≤ x < 1.2, 0.5 < y ≤ 0.70
When 1.2 ≤ x < 1.3, 0.5 < y ≤ 0.71
When 1.3 ≤ x < 1.6, 0.5 < y ≤ 0.72
When 1.6 ≤ x < 2.0, 0.5 < y ≤ 0.73
When 2.0 ≤ x, 0.5 < y ≤ 0.74;
TABLE 2
When 0.4 ≤ x < 0.5, 0.5 < y ≤ 0.51
When 0.5 ≤ x < 0.6, 0.5 < y ≤ 0.53
When 0.6 ≤ x < 0.7, 0.5 < y ≤ 0.55
When 0.7 ≤ x < 0.8, 0.5 < y ≤ 0.57
When 0.8 ≤ x < 0.9, 0.5 < y ≤ 0.58
When 0.9 ≤ x < 1.0, 0.5 < y ≤ 0.59
When 1.0 ≤ x < 1.1, 0.5 < y ≤ 0.61
When 1.1 ≤ x < 1.2, 0.5 < y ≤ 0.62
When 1.2 ≤ x < 1.3, 0.5 < y ≤ 0.63
When 1.3 ≤ x < 1.5, 0.5 < y ≤ 0.64
When 1.5 ≤ x < 1.7, 0.5 < y ≤ 0.65
When 1.7 ≤ x < 2.0, 0.5 < y ≤ 0.66
When 2.0 ≤ x < 2.7, 0.5 < y ≤ 0.67
When 2.7 ≤ x, 0.5 < y ≤ 0.68;
TABLE 3
When 0.5 ≤ x < 0.6, 0.5 < y ≤ 0.52
When 0.6 ≤ x < 0.7, 0.5 < y ≤ 0.53
When 0.7 ≤ x < 0.8, 0.5 < y ≤ 0.54
When 0.8 ≤ x < 0.9, 0.5 < y ≤ 0.56
When 0.9 ≤ x < 1.0, 0.5 < y ≤ 0.57
When 1.0 ≤ x < 1.2, 0.5 < y ≤ 0.59
When 1.2 ≤ x < 1.3, 0.5 < y ≤ 0.60
When 1.3 ≤ x < 1.4, 0.5 < y ≤ 0.61
When 1.4 ≤ x < 1.5, 0.5 < y ≤ 0.62
When 1.5 ≤ x < 1.7, 0.5 < y ≤ 0.63
When 1.7 ≤ x < 2.0, 0.5 < y ≤ 0.64
When 2.0 ≤ x < 2.5, 0.5 < y ≤ 0.65
When 2.5 ≤ x, 0.5 < y ≤ 0.66;
and
TABLE 4
When 0.5 ≤ x < 0.6, 0.5 < y ≤ 0.52
When 0.6 ≤ x < 0.7, 0.5 < y ≤ 0.53
When 0.7 ≤ x < 0.8, 0.5 < y ≤ 0.54
When 0.8 ≤ x < 0.9, 0.5 < y ≤ 0.56
When 0.9 ≤ x < 1.0, 0.5 < y ≤ 0.57
When 1.0 ≤ x < 1.1, 0.5 < y ≤ 0.58
When 1.1 ≤ x < 1.2, 0.5 < y ≤ 0.59
When 1.2 ≤ x < 1.3, 0.5 < y ≤ 0.60
When 1.3 ≤ x < 1.4, 0.5 < y ≤ 0.61
When 1.4 ≤ x < 1.5, 0.5 < y ≤ 0.62
When 1.5 ≤ x < 1.7, 0.5 < y ≤ 0.63
When 1.7 ≤ x < 2.0, 0.5 < y ≤ 0.64
When 2.0 ≤ x < 2.7, 0.5 < y ≤ 0.65
When 2.7 ≤ x, 0.5 < y ≤ 0.66.
2 . The acoustic wave device according to claim 1 , further comprising a support substrate laminated on a surface of the high acoustic-velocity material layer opposite to a surface on a piezoelectric film side of the high acoustic-velocity material layer.
3 . The acoustic wave device according to claim 2 , further comprising:
a low acoustic-velocity film laminated between the high acoustic-velocity material layer and the piezoelectric film and made of a low acoustic-velocity material; wherein
the low acoustic-velocity material is a material in which an acoustic velocity of a bulk wave propagating therethrough is lower than an acoustic velocity of a bulk wave propagating through the piezoelectric film.
4 . The acoustic wave device according to claim 3 , wherein the low acoustic-velocity material is made of silicon oxide.
5 . The acoustic wave device according to claim 2 , wherein the support substrate is made of the high acoustic-velocity material, and the support substrate and the high acoustic-velocity material layer are integrated with each other.
6 . The acoustic wave device according to claim 1 , wherein the support substrate is made of Si.
7 . The acoustic wave device according to claim 1 , wherein the high acoustic-velocity material is made of silicon nitride.
8 . The acoustic wave device according to claim 1 , wherein the piezoelectric film is made of lithium tantalate.
9 . An acoustic wave device comprising:
a high acoustic-velocity material layer made of a high acoustic-velocity material;
a piezoelectric film directly or indirectly on the high acoustic-velocity material layer; and
an IDT electrode on the piezoelectric film; wherein
the high acoustic-velocity material is a material in which an acoustic velocity of a bulk wave propagating therethrough is higher than an acoustic velocity of an acoustic wave propagating through the piezoelectric film;
the acoustic wave device further includes a dielectric film between the IDT electrode and the piezoelectric film; and
the dielectric film is made of one of silicon oxide, silicon nitride, alumina, and amorphous silicon, and when a wavelength determined based on an electrode finger pitch of the IDT electrode is denoted as λ, duty of the IDT electrode is denoted as y, and a film thickness normalized by the wavelength λ of the dielectric film is denoted as x (%), the duty y of the IDT electrode and the film thickness x of the dielectric film are within a hatched area in FIG. 4 when the dielectric film is made of silicon oxide, FIG. 5 when the dielectric film is made of silicon nitride, FIG. 6 when the dielectric film is made of alumina, and FIG. 7 when the dielectric film is made of amorphous silicon.
10 . The acoustic wave device according to claim 9 , further comprising a support substrate laminated on a surface of the high acoustic-velocity material layer opposite to a surface on a piezoelectric film side of the high acoustic-velocity material layer.
11 . The acoustic wave device according to claim 10 , further comprising:
a low acoustic-velocity film laminated between the high acoustic-velocity material layer and the piezoelectric film and made of a low acoustic-velocity material; wherein
the low acoustic-velocity material is a material in which an acoustic velocity of a bulk wave propagating therethrough is lower than an acoustic velocity of a bulk wave propagating through the piezoelectric film.
12 . The acoustic wave device according to claim 11 , wherein the low acoustic-velocity material is made of silicon oxide.
13 . The acoustic wave device according to claim 10 , wherein the support substrate is made of the high acoustic-velocity material, and the support substrate and the high acoustic-velocity material layer are integrated with each other.
14 . The acoustic wave device according to claim 9 , wherein the support substrate is made of Si.
15 . The acoustic wave device according to claim 9 , wherein the high acoustic-velocity material is made of silicon nitride.
16 . The acoustic wave device according to claim 9 , wherein the piezoelectric film is made of lithium tantalate.