A semiconductor device manufacturing method having a multi-layered wiring structure comprises the steps of forming an insulating film over a semiconductor substrate, coating resist on the insulating film, forming a wiring pattern window in the resist, forming a wiring recess by etching the insulating film via the window, removing the resist, removing a reaction product existing on the insulating film by exposing the insulating film to a plasma atmosphere using an inactive gas, and burying a metal film into the wiring recess to form a wiring.