A method of forming a silica-based film includes:applying a composition for forming an insulating film for a semiconductor device, which is cured by using heat and ultraviolet radiation, to a substrate to form a coating; heating the coating; and applying heat and ultraviolet radiation to the coating to effect a curing treatment. The composition includes: a hydrolysis-condensation product produced by hydrolysis and condensation of at least one silane compound selected from the group consisting of compounds shown by the following general formula (A), and at least one silane compound selected from the group consisting of compounds shown by the following general formula (B) and compounds shown by the following general formula (C); and an organic solvent, ##STR00001##