Abstract: A high-accuracy high-stability capacitor type pressure sensor which eliminates a parasitic capacitance between a reference capacitor and a semiconductor substrate. A capacitor type pressure sensor comprising, on a semiconductor substrate 10, an active capacitor 100 whose capacitance varies as the surrounding pressure varies, a reference capacitor 200 whose capacitance will not vary substantially as the surrounding pressure varies, and a circuit which is electrically connected to both said active and reference capacitors 100 and 200, detects the difference or ratio thereof, and uses the potential of a semiconductor substrate, wherein an electrode 30a of said reference capacitor is formed on the semiconductor substrate 10 with a dielectric 20 therebetween.