Decoupling capacitors and semiconductor integrated circuit

Abstract

VSSis provided to a gate portionand VDDis provided to a source portionand a drain portionof a MOS transistor which constitutes a decoupling capacitor, and a potential NWVDDdifferent from that provided to the source portionand the drain portionis provided to a substrate portion. If NWVDDis set higher than VDD, a depletion layeris spread, so that a leakage current can be reduced instead of reducing a capacitance of the decoupling capacitor. In addition, if NWVDDis set lower than VDDso as not to cause latchup, the depletion layeris reduced, so that the capacitance of the decoupling capacitor can be increased. By changing the potential NWVDDprovided to the substrate portion, a capacitance value and a leakage current value of the decoupling capacitor can be controlled. Thereby making it possible to achieve a decoupling capacitor capable of controlling the capacitance value and the leakage current value and also having excellent response characteristics.