First and second wirings are formed on a first insulating film. Each of the wirings is arranged so that a conductive film, a silicon oxide film and a silicon nitride film are laminated. Thereafter, a silicon oxide insulating film on the whole surface. The silicon oxide insulating film is etched so that a contact hole is formed between the first and second wirings. Since the silicon oxide film and the silicon nitride film exist on the conductive film of each wiring, the conductive film is not exposed at the time of etching. Thereafter, an insulating film is formed on a side wall of the contact hole, and the conductive film exposed through the contact hole is covered by the insulating film.