| 摘要 |
[Problem] In a SAW device using a quartz crystal substrate, prevent the deterioration of Q factor due to the difference in the peak frequency between the radiation conductance of an IDT and the reflection coefficient of a reflector. [Means to Solve the Problem] A surface acoustic wave (SAW) device includes a piezoelectric substrate made of a quartz crystal flat plate where a cut angle of a rotated Y-cut quartz substrate is set in −64.0°<&thetas;<−49.3° with a crystalline Z axis and a propagation direction of the surface acoustic wave is set at 90°±5° with a crystalline X axis, an interdigital transducer (IDT) formed on the piezoelectric substrate and reflectors disposed at both sides of the IDT, wherein an exciting wave is SH wave, an electrode film thickness “H/λ” normalized by a wavelength of the IDT is 0.05≦̸H/λ≦̸0.07 where “λ” is a wavelength of the exciting SAW, and a ratio of an electrode pitch between the IDT and the reflector “Lt/Lr” is set to satisfy the following formula: 31.50×(H/λ)2−4.435×(H/λ)+1.133≦̸Lt/Lr≦̸−3.000×(H/λ)2+0.500×(H/λ)+0.9796 where “Lt” is the electrode pitch of the IDT and “Lr” is the electrode pitch of the reflector.
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