This invention relates to a method of film formation in which, when a silicon oxide film (a NSG film: a Non-doped Silicate Glass) is formed on a substrate having a recess by a CVD method using a mixed gas containing TEOS and ozone, surface dependency on the substrate is eliminated to embed a silicon oxide film into the recess of the surface. The invention includes forming a phosphorus containing insulating film as a base layer on the surface of a substrate and forming a silicon-containing insulating film on the phosphosilicate glass film by the chemical vapor deposition method, using a mixture of a ozone-containing gas and a silicon-containing gas.