A method of forming a nitride film wherein (a) a silane-based gas is supplied to a processing chamber through a gas supply port; (b) a nitrogen radical gas from a radical generator is supplied to the processing chamber through a radical gas pass-through port; and (c) the silane-based gas supplied in (a) is reacted with the nitrogen radical gas supplied in (b), without causing a plasma phenomenon in the processing chamber, to form a nitride film on a wafer.