A method of filling a recess with an insulation film includes: introducing an alkoxysilane or aminosilane precursor containing neither a Si—C bond nor a C—C bond into a reaction chamber where a substrate having an irregular surface including a recess is placed; and depositing a flowable Si-containing insulation film on the irregular surface of the substrate to fill the recess therewith by plasma reaction at −50° C. to 100° C.