Patent ID: 6921936

Claim:
A pn varactor using pn junctions as variable capacitance capacitor, the pn varactor comprising: a one-conduction-type semiconductor region arranged in a semiconductor substrate; a first other-conduction-type semiconductor region and a second other-conduction-type semiconductor region arranged both sides of the one-conduction-type semiconductor region and constituting pn junctions together with the one-conduction-type semiconductor region; a pseudo-gate pattern on the one-conduction-type semiconductor region; a first dummy pattern arranged above of opposite end of the pseudo-gate pattern on the first other-conduction-type semiconductor region; and a second dummy pattern arranged above of opposite end of the pseudo-gate pattern on the second other-conduction-type semiconductor region, wherein the pseudo-gate pattern, the one-conduction-type semiconductor region, the first other-conduction-type semiconductor region, and the second other-conduction-type semiconductor region constitute pseudo-FET structure, and wherein a pn junction of the one-conduction-type semiconductor region and the first other-conduction-type semiconductor region and a pn junction of the one-conduction-type semiconductor region and the second other-conduction-type semiconductor region are used as a first varactor and a second varactor, respectively, electrostatic capacitances of which vary depending on potential applied to the one-conduction-type semiconductor region.