A silicon film forming method of forming a silicon film in a recess with respect to a target substrate having on its surface an insulating film in which the recess is formed. The method includes (a) forming a first silicon film filling the recess by supplying a Silicon raw material gas onto the target substrate, (b) subsequently, etching the first silicon film by supplying a halogen-containing etching gas onto the target substrate such that surfaces of the insulating film on the target substrate and on an upper portion of an inner wall of the recess are exposed and such that the first silicon film remains in a bottom portion of the recess, and (c) subsequently, growing a second silicon film in a bottom-up growth manner on the first silicon film that remains in the recess by supplying a Silicon raw material gas onto the target substrate after the etching.