A decoupling capacitor is disclosed that has an n-type portion and a p-type portion in a semiconductor. The decoupling capacitor is formed of an NFET transistor and a PFET transistor, the PFET transistor being substantially formed in the n-type portion and the NFET transistor being substantially formed in the p-type portion, a boundary between the n-type portion and the p-type portion being substantially straight. The transistors are arranged such that a source and drain of the PFET transistor are connected to a high voltage rail and a source and drain of the NFET transistor are connected to a low voltage rail.