Method of manufacturing semiconductor device with capacitor and transistor

Abstract

The invention is to prevent dielectric breakdown of a capacitor in a semiconductor device having the capacitor and a MOS transistor formed on a same semiconductor substrate. A SiOfilm that is to be a gate insulation film of a high voltage MOS transistor is formed on a whole surface of a P-type semiconductor substrate. A photoresist layer is selectively formed in a high voltage MOS transistor formation region and on a part of a SiOfilm covering edges of trench isolation films adjacent to a capacitor formation region, and the SiOfilm is removed by etching using this photoresist layer as a mask. Since the photoresist layer functions as a mask in this etching, the edges of the trench isolation films adjacent to the capacitor are not cut too deep. The SiOfilm remaining in this etching and a SiOfilm to be formed thereafter form a capacitor insulation film.