A method of manufacturing a semiconductor device includes forming a field plate on an insulating film covering a transistor, the field plate being electrically coupled to a gate of the transistor via the insulating film, and the transistor being located on a substrate, forming a silicon nitride protective film covering the insulating film and the field plate, forming a silicon oxide base film on the silicon nitride protective film, and forming a MIM capacitor on the silicon oxide base film. The MIM capacitor includes a first electrode, a dielectric film and a second electrode which are stacked in an order. Forming the MIM capacitor includes performing wet etching on the silicon oxide base film on the field plate after forming the dielectric film.