| 摘要 |
PROBLEM TO BE SOLVED: To provide a semiconductor device having a low capacitance, a low resistance and a large capacity variation ratio. SOLUTION: An epitaxial layer is formed in a principal plane of a first conductivity-type semiconductor substrate, and this epitaxial layer is partitioned into a first region and a second region by an element isolation region. On a front surface of the epitaxial layer in the first region, there is provided a PN junction part which has a second conductivity-type semiconductor layer and constitutes a variable capacitance. On the front surface of the epitaxial layer in the second region, there is provided the PN junction part as a stationary capacitance having the second conductivity-type semiconductor layer whose low portion is formed more adjacent to the semiconductor substrate than the second conductivity-type semiconductor layer constituting a PN junction of the variable capacitance. A rear face of the semiconductor substrate is connected to a control voltage terminal. The second conductivity-type semiconductor layer constituting the PN junction of the variable capacitance is connected to a first signal terminal. The second conductivity-type semiconductor layer constituting the PN junction of the stationary capacitance is connected to a second signal terminal. Thereby, a variable filter circuit is constituted. COPYRIGHT: (C)2009,JPO&INPIT
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