A method of forming a silicon film in a recess formed in a target substrate includes: preparing a target substrate having a recess in which a plurality of different bases is exposed; forming an atomic layer seed on at least an inner surface of the recess by sequentially supplying a raw material gas adapted to the plurality of different bases and a reaction gas reacting with the raw material gas to the target substrate one or more times while heating the target substrate to a first temperature; and forming a silicon film on a surface of the atomic layer seed so as to fill the recess by supplying a first silicon raw material gas to the target substrate while heating the target substrate to a second temperature.