Disclosed is a method of manufacturing a semiconductor device including: performing a pre-process to a substrate, on a surface of which a metal film or a GST film is formed, such that a first film is formed on the metal film or the GST film by executing at least one cycle of alternately performing (i) supplying a first processing gas, and (ii) supplying a second processing gas that is not activated by plasma excitation; and performing a formation process to the substrate to which the pre-process has been performed such that a second film is formed on the first film by executing at least one cycle of alternately (i) supplying the first processing gas, and (ii) supplying the second processing gas that is activated by plasma excitation.