| 摘要 |
A surface acoustic wave element has a small energy loss and when it is used in a filter device, suppresses a spurious component occurring near the resonant frequency of a principal response and improves the frequency characteristic near the pass band of the filter device. The surface acoustic wave element includes a piezoelectric substrate, a comb-shaped electrode, and an insulating film. The comb-shaped electrode is disposed on the piezoelectric substrate. The insulating film is disposed so as to cover the piezoelectric substrate and the comb-shaped electrode. Where lambda is the wavelength of an elastic wave that propagates in the piezoelectric substrate and h is the difference between the maximum and minimum values of a thickness dimension from the top surface of the piezoelectric substrate to the top surface of the insulating film, 0.01@h/lambda@0.03 is satisfied.
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