MIS type capacitor having reduced change in capacitance when biased in forward and reverse directions

摘要

An MIS capacitor for bipolar integrated circuits includes an island region of one conductivity type, a first semiconductor layer of one conductivity type formed in the island region, an insulating layer provided on the first semiconductor layer, a capacitor electrode provided on the insulating layer to provide an MIS capacitor element, and a second semiconductor layer of an opposite conductivity type for providing a PN junction with the first semiconductor layer. When the MIS capacitor element is reverse biased, majority carriers of the second semiconductor layer are supplied to a depletion layer generated in the first semiconductor layer, thereby providing an MIS capacitor having an approximately constant capacitance even if it is biased in a forward or reverse direction.