A method for manufacturing a semiconductor device includes: the first step of forming, in an insulating film provided on a substrate, a recess that is porositized at least at inner walls; the second step of forming an alloy layer made of copper and a metal other than copper so as to cover the inner walls of the recess; the third step of burying a conductive layer made primarily of copper in the recess provided with the alloy layer; the fourth step of subjecting the thus treated substrate to thermal treatment to cause the metal in the alloy layer to react with a constituent component of the insulating film to form a barrier film made of a metal compound having Cu diffusion barrier properties.