A method of forming a dielectric film having Si—C bonds and/or Si—N bonds on a semiconductor substrate by cyclic deposition, includes: (i) conducting one or more cycles of cyclic deposition in a reaction space wherein a semiconductor substrate is placed, using a Si-containing precursor and a reactant gas; and (ii) before or after step (i), applying a pulse of RF power to the reaction space while supplying a rare gas and a treatment gas without supplying a Si-containing precursor, whereby a dielectric film having Si—C bonds and/or Si—N bonds is formed on the semiconductor substrate.