| 摘要 |
PROBLEM TO BE SOLVED: To provide a piezoelectric resonator which is capable of yielding a wide-band▵f or high Q-factor, with regard to the piezoelectric resonator, production method thereof, filter using the same, duplexer and communications device. SOLUTION: The present invention relates to a piezoelectric resonator, including a substrate; a lower electrode provided above the substrate; a piezoelectric member 101 provided above the lower electrode; an upper electrode 102 provided above the piezoelectric member 101; and a cavity 104 provided below a vibration member 110 consisting of the lower electrode 103, the piezoelectric member, and the upper electrode. When the resonance frequency of vibration with a thickness of the vibration member, being half the wavelength, is set as fr1, the average of ultrasonic velocity in a material forming the cavity is set as Vc2, and a value determined, based on the resonance frequency fr1 and the average of ultrasonic velocity Vc2, isλc (=Vc2/fr1), a depth t2 of the cavity is set as shown by Formula (1), where (n) is an arbitrary natural number. COPYRIGHT: (C)2005,JPO&NCIPI
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