The present invention relates to a semiconductor device manufacturing method for forming an interlayer insulating film having a low dielectric constant by coating a copper wiring. The low dielectric constant insulating film is formed by reaction of a plasma of a film-forming gas containing an oxygen-containing gas of N2O, H2O, or CO2, ammonia (NH3), and at least one of an alkyl compound having a siloxane bond and methylsilane (SiHn(CH3)4−n: n=0, 1, 2, 3).