ELASTIC SURFACE WAVE DEVICE, MODULE DEVICE, OSCILLATION CIRCUIT, AND ELASTIC SURFACE WAVE DEVICE FABRICATION METHOD

摘要

An objective is to provide an SH wave type SAW device which is a surface acoustic wave device using a quartz substrate and which is small in size and has a large Q value and excellent frequency aging characteristics. An SH wave type surface acoustic wave device includes a piezoelectric substrate and an IDT electrode provided on the piezoelectric substrate and constituted of Al or an alloy mainly containing Al and that uses a SH wave as an excitation wave. The piezoelectric substrate is a crystal plate in which a cut angle ¸ of a rotary Y cut quartz substrate is set in a range of -64.0° < ¸ < -49.3° and in which a surface acoustic wave propagation direction is set at 90° ± 5° with respect to a crystal axis X. In the SH wave type surface acoustic wave device, an electrode film thickness H/» standardized by a wavelength of the IDT electrode is 0.04 < H/» < 0.12, where » is a wavelength of the surface acoustic wave to be excited, and a main surface of the piezoelectric substrate is etched by a thickness of 0.002 µm or more.