Abstract: To provide a deposition process whereby a seamless Si-containing film having a small number of voids can be formed on a substrate having a fine trench at a lower temperature. A method for forming an Si-containing film forms an Si-containing film on a substrate by a chemical vapor deposition process, wherein the chemical vapor deposition process includes a step (a) that reacts a first feed gas having one or more Si—Si bonds in a chemical vapor deposition chamber in the presence of a Lewis base catalyst.