Surface acoustic wave device, module device, oscillation circuit, and method for manufacturing surface acoustic wave device

An SH wave type surface acoustic wave device, comprising:

• a piezoelectric substrate;
• and
• an IDT electrode provided on the piezoelectric substrate and constituted of Al or an alloy mainly containing Al, wherein:
• the device uses a SH wave as an excitation wave;
• the piezoelectric substrate is a crystal plate in which a cut angle θ of a rotary Y cut quartz substrate is set in a range of −64.0°<θ<−49.3° in a counter-clockwise direction from a crystal axis Z and in which a surface acoustic wave propagation direction is set at 90°±5° with respect to a crystal axis X;
• an electrode film thickness H/λ standardized by a wavelength of the IDT electrode is 0.04<H/λ<0.12, where λ 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.

An SH wave type surface acoustic wave device, comprising:

• a piezoelectric substrate;
• and
• an IDT electrode provided on the piezoelectric substrate and constituted of Al or an alloy mainly containing Al, wherein:
• the deice uses a SH wave as an excitation wave;
• the piezoelectric substrate is a crystal plate in which a cut angle θ of a rotary Y cut quartz substrate is set in a range of −61.4°<θ<−51.1° in a counter-clockwise direction from a crystal axis Z and in which a surface acoustic wave propagation direction is set at 90°±5° with respect to a crystal axis X and has an etched trace on a surface thereof, the etched trace being formed by wet etching and running from one side to the other side on the surface;
• an electrode film thickness H/λ standardized by a wavelength of the IDT electrode is 0.05<H/λ<0.10, where λ is a wavelength of the surface acoustic wave to be excited;
• and
• the IDT electrode is provided on the surface having the etched trace of the piezoelectric substrate.