After forming a stopper film on a semiconductor substrate having a copper wiring layer therein, an interlayer insulating film made of a low dielectric constant material is formed on the stopper film. Then, after forming a capping film on the interlayer insulating film, a resist film having a predetermined pattern is formed on the capping film. The capping film and the interlayer insulating film are etched using the resist film as a mask to form an opening reaching the stopper film. After that, the stopper film exposed by the opening is etched, with the resist film left in place, to form a via hole. Then, the resist film is removed by ashing.