US 2004/0201045 A1Published application

Voltage-controlled capacitive element and semiconductor integrated circuit

AssigneeNEC Electronics Corporation

InventorsSusumu Kurosawa, Yuki Fujimoto, Yasutaka Nakashiba

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Abstract

An N well is disposed in the upper surface of a P type substrate, a gate insulating film and a gate electrode are disposed thereon, and the gate electrode is connected to a gate terminal. Two p+ diffusion regions are placed in two areas in the surface of the N well sandwiching the gate electrode, and the p+ diffusion regions are connected to a ground potential wiring. Further, an n+ diffusion region is disposed in the surface of the N well, and is connected to a well terminal. Accordingly, capacitance is generated between the gate electrode and the N well of a varactor element. When the potential of the gate terminal is decreased, the two p+ diffusion regions absorb positive holes serving as minority carriers from a channel region.

Claims8

Dependent claims

A voltage-controlled capacitive element comprising:

a substrate;
a first conductivity region which is disposed in the surface of said substrate and which is applied a first potential;
a second conductivity region which is disposed in part of the surface of said first conductivity region and which is applied a second potential which does not generate a forward pn junction between said first conductivity region and said second conductivity region;
an insulating film disposed on said first conductivity region and said second conductivity region;
and
a conductive film which is disposed on said insulating film at an area which is at least of a part of an area except an area directly over said second conductivity region and which is applied a third potential,
wherein capacitance is generated by said first conductivity region, said insulating film, and said conductive film.

4 more elements

Dependencies are inferred from the claim text.