| 摘要 |
PROBLEM TO BE SOLVED: To provide a filter that achieves a size-reduction without impairing mechanical strength of an electrode, having a hollow structure, while suppressing effects caused by a lateral-mode unwanted wave of a piezoelectric thin-film resonator in the filter using the piezoelectric thin-film resonator. SOLUTION: The filter includes a plurality of piezoelectric thin-film resonators S1-S4 respectively in which a piezoelectric film 3 is sandwiched by a lower electrode 2, formed on a substrate, and an upper electrode 4. Each piezoelectric thin-film resonator S1-S4 is configured such that the outline shape of each electrode region 4a-4d, on which the upper electrode 4 and the lower electrode 2 are superposed, includes a curved line. The piezoelectric thin-film resonators, adjacent to each other, of the plurality of piezoelectric thin-film resonators S1-S4 are configured such that each outline shape of the electrode regions arranged adjacently opposite to each other is formed into a complementary shape. COPYRIGHT: (C)2010,JPO&INPIT
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