| 摘要 |
A piezoelectric thin-film resonator includes a substrate, a lower electrode arranged on the substrate, a piezoelectric film arranged on the lower electrode, and an upper electrode arranged on the piezoelectric film. A region in which the upper electrode overlaps with the lower electrode through the piezoelectric film has an elliptical shape, and a condition such that 1<a/b<1.9 is satisfied where a is a main axis of the elliptical shape, and b is a sub axis thereof.
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