A method of manufacturing a semiconductor device includes forming a flash memory cell in a first region, forming a first electrode of a capacitor in a second region, forming a first silicon oxide film, a silicon nitride film, and a second silicon oxide film in this order as a second insulating film, removing the silicon nitride film and the second silicon oxide film in a partial region of the first electrode, wet-etching a first insulating film and the second insulating film in the third region, forming a second electrode of the capacitor, and etching and removing the first silicon oxide film in the partial region.