| 摘要 |
A filter includes multiple piezoelectric thin-film resonators (S11,S12,S13,S14,P11,P12,P13,P14) each having a substrate (11), a lower electrode (13) formed on the substrate (11), a piezoelectric film (14) formed on the lower electrode (13), and an upper electrode (15) provided on the piezoelectric film (14) so that the upper electrode (15) and the lower electrode (13) face each other across the piezoelectric film (14).
The piezoelectric thin-film resonator (S11,S12,S13,S14,P11,P12,P13,P14) are of two types:
a) a first type (S11,S14,P11,P14) where at least a part (28) of an outer curved portion of the piezoelectric film (14) is located further out than an outer curved portion (26) of a region (24) in which the upper electrode (15) and the lower electrode (13) face each other across the piezoelectric film (14); and
b) a second type (Sl2,S13,P12,P13) in which at least a part of an outer curved portion of the piezoelectric film (14) coincides with an outer curved portion (26) of a region (24) in which the upper electrode (15) and the lower electrode (13) face each other across the piezoelectric film (14) or is further inside the outer curved portion (26) of the region (24).
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