Surface acoustic wave device and method of manufacturing the same
An end-surface-reflection surface acoustic wave device, which reflects a surface acoustic wave between first and second end surfaces facing each other, includes a support substrate, an intermediate layer, a piezoelectric layer, and an IDT electrode. The first end surface is located at one end portion in a surface-acoustic-wave propagation direction and extends from a main surface of the piezoelectric layer to at least a portion of the intermediate layer. The second end surface is located at the other end portion in the surface-acoustic-wave propagation direction and extends from the main surface of the piezoelectric layer to at least a portion of the intermediate layer. The support substrate includes support substrate portions that are located outside the first and second end surfaces in the surface-acoustic-wave propagation direction.
1. An end-surface-reflection surface acoustic wave device comprising:
a first end surface and a second end surface facing the first end surface and that reflects a surface acoustic wave at the first and second end surfaces;
a support substrate;
an intermediate layer disposed on the support substrate;
a piezoelectric layer disposed on the intermediate layer and including a main surface; and
an IDT electrode disposed on the main surface of the piezoelectric layer; wherein
the first end surface is located at one end portion in a surface-acoustic-wave propagation direction and extends from the main surface of the piezoelectric layer into at least a portion of the intermediate layer;
the second end surface is located at the other end portion in the surface-acoustic-wave propagation direction and extends from the main surface of the piezoelectric layer into at least a portion of the intermediate layer; and
the support substrate includes support substrate portions that are located outside the first and second end surfaces in the surface-acoustic-wave propagation direction.
2. The surface acoustic wave device according to claim 1 , wherein the support substrate defines a mount substrate.
3. The surface acoustic wave device according to claim 1 , wherein the first and second end surfaces each extend from the main surface of the piezoelectric layer into only a portion of the intermediate layer.
4. The surface acoustic wave device according to claim 1 , wherein
the support substrate includes a main surface that is in contact with the intermediate layer; and
the first and second end surfaces each extend from the main surface of the piezoelectric layer to the main surface of the support substrate.
5. The surface acoustic wave device according to claim 1 , wherein
the support substrate includes a first main surface that is in contact with the intermediate layer and a second main surface that faces the first main surface; and
the first and second end surfaces each extend from the main surface of the piezoelectric layer to a position between the first main surface and the second main surface of the support substrate.
6. The surface acoustic wave device according to claim 1 , wherein the intermediate layer has a multi-layer structure including a plurality of layers that are stacked.
7. The surface acoustic wave device according to claim 6 , wherein the first and second end surfaces each extend from the main surface of the piezoelectric layer to a portion of one of the plurality of layers of the intermediate layer.
8. The surface acoustic wave device according to claim 6 , wherein a layer of the plurality of layers of the intermediate layer that is nearest to the support substrate in a stacking direction is made of silicon oxide.
9. The surface acoustic wave device according to claim 8 , wherein the first and second end surfaces each extend from the main surface of the piezoelectric layer to a portion of the layer of the plurality of layers of the intermediate layer that is nearest to the support substrate.
10. The surface acoustic wave device according to claim 8 , wherein the support substrate is made of at least one material selected from the group consisting of silicon, sapphire, LiTaO 3 , LiNbO 3 , and glass.
11. The surface acoustic wave device according to claim 1 , wherein a groove is provided in the piezoelectric layer and the intermediate layer, the groove extending through the piezoelectric layer and at least a portion of the intermediate layer and including a first side surface, and the first side surface of the groove includes the first end surface.
12. The surface acoustic wave device according to claim 11 , wherein
the groove includes a second side surface facing the first side surface;
the IDT electrode is a first IDT electrode, and the surface acoustic wave device further includes a second IDT electrode that is adjacent to the first IDT electrode with the groove provided therebetween in the surface-acoustic-wave propagation direction; and
the second side surface of the groove includes an end surface that reflects a surface acoustic wave that is excited by the second IDT electrode.
13. The surface acoustic wave device according to claim 1 , wherein
the IDT electrode is a first IDT electrode, and the surface acoustic wave device further includes a second IDT electrode that is adjacent to the first IDT electrode in the surface-acoustic-wave propagation direction; and
a plurality of grooves that are adjacent to each other in the surface-acoustic-wave propagation direction are provided between the first IDT electrode and the second IDT electrode, a side surface of one of the plurality of grooves that is nearest to the first IDT electrode includes the first end surface, and a side surface of one of the grooves nearest to the second IDT electrode includes an end surface that reflects a surface acoustic wave that is excited by the second IDT electrode.
14. The surface acoustic wave device according to claim 1 , wherein the support substrate, the intermediate layer, and the piezoelectric layer are made of different materials.
15. The surface acoustic wave device according to claim 1 , wherein the intermediate layer is made of SiO 2 .
16. The surface acoustic wave device according to claim 6 , wherein the plurality of layers of the intermediate layer include low-acoustic-impedance layers and high-acoustic-impedance layers.
17. The surface acoustic wave device according to claim 16 , wherein the low-acoustic-impedance layers and high-acoustic-impedance layers are alternately stacked.
18. The surface acoustic wave device according to claim 16 , wherein at least one of low-acoustic-impedance layers is closer to the piezoelectric layer than the high-acoustic-impedance layers.
19. A method of manufacturing the surface acoustic wave device according to claim 1 , the method comprising:
a step of forming a stacked body in which the support substrate, the intermediate layer, the piezoelectric layer, and the IDT electrode are stacked in this order; and
a step of removing at least a portion of the piezoelectric layer and the intermediate layer by etching so as to form the first and second end surfaces.
20. The method of manufacturing the surface acoustic wave device according to claim 19 , further comprising a step of removing a portion of the support substrate by dicing so that the first and second end surfaces each extend from the main surface of the piezoelectric layer to a portion of the support substrate.