Abstract: A piezoelectric bulk wave device includes a piezoelectric substrate including a support including a silicon substrate and a piezoelectric layer on the support, first and second wire electrodes on the piezoelectric substrate, and a functional electrode on the piezoelectric layer, connected to at least one of the first and second wire electrodes, and including multiple electrodes. At least two of the first and second wire electrodes, and the multiple electrodes include first and second electrode films connected to different potentials. A plane orientation of the silicon substrate is (111), and ? in Euler angles (?, ?, ?) of the silicon substrate is an angle within a range of about 10°+120°×n???about 50°+120°×n or about 70°+120°×n???about 110°+120°×n, where n is any integer.

Abstract: An acoustic wave device includes a support substrate, a piezoelectric layer, a functional electrode, a first trace, a second trace, and an attenuation layer. The piezoelectric layer is located on the support substrate and includes first and second main surfaces on opposite sides. The functional electrode is located on the first or second main surface of the piezoelectric layer. The first trace is located on the piezoelectric layer and connected to the functional electrode. The second trace is located on the piezoelectric layer and faces the first trace. The first and second traces are connected to different potentials. The attenuation layer is located between the first trace and the second trace when viewed in plan. The attenuation layer is made of a dielectric material lower in density than the piezoelectric layer.