To provide a semiconductor device including a thin film bulk wave element whose resonance frequency is adjustable, which can be made more small-sized.
The semiconductor device 11 is provided with: the thin film bulk wave element 10; a resonance frequency adjustment section 11; a wire 12; a silicon oxide layer 13; and a silicon substrate 14. The thin film bulk wave element 10 is configured such that an upper electrode 100 and a lower electrode 101 sandwich a piezoelectric thin film 102. A cavity 140 is provided to a part of the substrate 14 opposed to the piezoelectric thin film 102 with the silicon oxide layer 13 in-between. The resonance frequency adjustment section 11 is provided with a variable voltage power supply 110 and a variable capacitance diode 111. The variable capacitance diode 111 includes a p type region 111p and an n type region 111n and the variable capacitance diode 111 adjusts the resonance frequency of the thin film bulk wave element 10 by the application of a voltage to the p type region 111p, the voltage being lower than the voltage applied to the n type region 111n so as to vary the capacitance of a thus formed pn junction.
YOSHIOKA KOICHI
TAKEDA KATSUTOSHI
FUJITA MASAYUKI
KOBAYASHI TAIZO
WAKIZAKA KENICHIRO
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