Piezoelectric device
A piezoelectric device includes a support substrate, an intermediate layer on the support substrate in a first region, a piezoelectric layer on the intermediate layer, a functional element on the piezoelectric layer, and an insulating layer. The insulating layer is located on the support substrate in a second region adjacent to the first region. A surface roughness of the support substrate in the second region is greater than a surface roughness of the support substrate in the first region.
1 . A piezoelectric device comprising:
a support substrate;
an intermediate layer on the support substrate in a first region;
a piezoelectric layer on the intermediate layer;
a functional element on the piezoelectric layer; and
an insulating layer on the support substrate in a second region adjacent to the first region; wherein
a surface roughness of the support substrate in the second region is greater than a surface roughness of the support substrate in the first region.
2 . The piezoelectric device according to claim 1 , wherein
the second region includes a first portion adjacent to the first region and a second portion farther away from the first region than the first portion; and
a surface roughness of the support substrate in the first portion is greater than a surface roughness of the support substrate in the second portion.
3 . The piezoelectric device according to claim 2 , wherein
a thickness of the support substrate in the second region is smaller than a thickness of the support substrate in the first region; and
the support substrate includes an inclined region between the first region and the second region.
4 . The piezoelectric device according to claim 2 , wherein
the intermediate layer includes:
a high-acoustic-velocity layer on the support substrate and through which a bulk acoustic wave with a velocity higher than a velocity of a bulk acoustic wave that propagates to the piezoelectric layer propagates; and
a low-acoustic-velocity layer between the high-acoustic-velocity layer and the piezoelectric layer and through which a bulk acoustic wave with a velocity lower than a velocity of an acoustic wave that propagates to the piezoelectric layer propagates.
5 . The piezoelectric device according to claim 1 , wherein
a thickness of the support substrate in the second region is smaller than a thickness of the support substrate in the first region; and
the support substrate includes an inclined region between the first region and the second region.
6 . The piezoelectric device according to claim 5 , wherein
the intermediate layer includes:
a high-acoustic-velocity layer on the support substrate and through which a bulk acoustic wave with a velocity higher than a velocity of a bulk acoustic wave that propagates to the piezoelectric layer propagates; and
a low-acoustic-velocity layer between the high-acoustic-velocity layer and the piezoelectric layer and through which a bulk acoustic wave with a velocity lower than a velocity of an acoustic wave that propagates to the piezoelectric layer propagates.
7 . The piezoelectric device according to claim 1 , wherein
the intermediate layer includes:
a high-acoustic-velocity layer on the support substrate and through which a bulk acoustic wave with a velocity higher than a velocity of a bulk acoustic wave that propagates to the piezoelectric layer propagates; and
a low-acoustic-velocity layer between the high-acoustic-velocity layer and the piezoelectric layer and through which a bulk acoustic wave with a velocity lower than a velocity of an acoustic wave that propagates to the piezoelectric layer propagates.