SEMICONDUCTOR DEVICE MANUFACTURING METHOD, SUBSTRATE PROCESSING APPARATUS, AND NON-TRANSITORY RECORDING MEDIUM

A method of manufacturing a semiconductor device includes: accommodating a substrate having an oxide film formed thereon into a processing chamber; supplying a process gas to the substrate; performing a preprocessing step in which the process gas is excited in a state that a pressure within the processing chamber is kept at a first pressure and an electric potential of the substrate is kept at a first electric potential; and performing a main processing step by which the process gas is excited in a state that the pressure within the processing chamber is kept at a second pressure and the electric potential of the substrate is kept at a second electric potential, wherein the first pressure is lower than the second pressure and the first electric potential is lower than the second electric potential.