| 摘要 |
The present invention provides a MOS-type variable capacitance element which can obtain a sufficient capacitance valuable width and, at the same time, can eliminate restrictions imposed on a control voltage range. A MOS-type variable capacitance element includes a MOS transistor in which an N well having polarity opposite to polarity of the P type is formed on a P type semiconductor substrate, a pair of source and drain regions are formed in the inside of the N well, an N-type high-concentration region is formed in the inside of the N well, a gate oxide film is formed on the N well, and a gate electrode is formed on the gate oxide film, a first electrode which connects the source and drain regions to a reference potential, a second electrode which is connected to the gate electrode, and a third electrode which is connected to the N well and applies a control voltage having polarity equal to polarity of the P type to the N well using the reference potential as a reference, wherein a variable capacitance element is provided between the second electrode and the third electrode.
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