Acoustic wave device with an IDT electrode including an outer layer
An acoustic wave device includes a piezoelectric substrate and an IDT electrode including electrode fingers, a barrier layer on the piezoelectric substrate, and a first layer on the barrier layer, and including Cu as a main component. The first layer includes a first principal surface on a side closest to the piezoelectric substrate, a second principal surface opposite to the first principal surface, and a side surface connected to the first principal surface and the second principal surface. The barrier layer covers the first principal surface 5 a and the side surface of the first layer. A thickness of a portion of the barrier layer covering the first principal surface of the first layer is smaller than a thickness of a portion of the barrier layer covering the side surface of the first layer.
1 . An acoustic wave device comprising:
a piezoelectric substrate; and
an IDT electrode including a plurality of electrode fingers, an outer layer on the piezoelectric substrate, and an electrode layer on the outer layer and including Cu as a main component; wherein
the electrode layer includes a first principal surface positioned on a side closest to the piezoelectric substrate, a second principal surface opposite to the first principal surface, and a side surface connected to the first principal surface and the second principal surface;
the outer layer covers the first principal surface and the side surface of the electrode layer; and
a thickness of a portion of the outer layer covering the first principal surface of the electrode layer is smaller than a thickness of a portion of the outer layer covering the side surface of the electrode layer.
2 . The acoustic wave device according to claim 1 , further comprising a protective film on the piezoelectric substrate and covering the IDT electrode.
3 . The acoustic wave device according to claim 1 , wherein the electrode layer is a first layer of the IDT electrode, and the IDT electrode further includes a second layer on the second principal surface of the first layer.
4 . The acoustic wave device according to claim 2 , wherein the electrode layer is a first layer of the IDT electrode, and the IDT electrode further includes a second layer on the second principal surface of the first layer.
5 . The acoustic wave device according to claim 1 , wherein the outer layer covers the first principal surface, the side surface, and the second principal surface of the electrode layer.
6 . The acoustic wave device according to claim 2 , wherein the outer layer covers the first principal surface, the side surface, and the second principal surface of the electrode layer.
7 . The acoustic wave device according to claim 1 , wherein the outer layer is made of a metal oxide.
8 . The acoustic wave device according to claim 2 , wherein the outer layer is made of a metal oxide.
9 . The acoustic wave device according to claim 3 , wherein the outer layer is made of a metal oxide.
10 . The acoustic wave device according to claim 5 , wherein the outer layer is made of a metal oxide.
11 . The acoustic wave device according to claim 7 , wherein the outer layer is made of an oxide of one metal selected from the group consisting of Mn, Al, Mg, and Sn.
12 . The acoustic wave device according to claim 8 , wherein the outer layer is made of an oxide of one metal selected from the group consisting of Mn, Al, Mg, and Sn.
13 . The acoustic wave device according to claim 9 , wherein the outer layer is made of an oxide of one metal selected from the group consisting of Mn, Al, Mg, and Sn.
14 . The acoustic wave device according to claim 10 , wherein the outer layer is made of an oxide of one metal selected from the group consisting of Mn, Al, Mg, and Sn.
15 . The acoustic wave device according to claim 11 , wherein the outer layer is made of the oxide of Mn.
16 . The acoustic wave device according to claim 12 , wherein the outer layer is made of the oxide of Mn.
17 . The acoustic wave device according to claim 13 , wherein the outer layer is made of the oxide of Mn.
18 . The acoustic wave device according to claim 14 , wherein the outer layer is made of the oxide of Mn.
19 . The acoustic wave device according to claim 1 , wherein the piezoelectric substrate includes a support substrate and a piezoelectric layer on the support substrate.
20 . The acoustic wave device according to claim 1 , further comprising a dielectric film between the piezoelectric substrate and the IDT electrode; wherein
when a wavelength specified by an electrode finger pitch of the IDT electrode is denoted by λ, a thickness of the dielectric film is about 1% or less of the wavelength λ.