A silicon-containing film is formed from a heat curable composition comprising (A) a silicon-containing compound obtained by effecting hydrolytic condensation of a hydrolyzable silicon compound in the presence of an acid catalyst, and substantially removing the acid catalyst from the reaction mixture, (B) a hydroxide or organic acid salt of lithium, sodium, potassium, rubidium or cesium, or a sulfonium, iodonium or ammonium compound, (C) an organic acid, and (D) an organic solvent. The silicon-containing film allows an overlying photoresist film to be patterned effectively. The composition is effective in minimizing the occurrence of pattern defects after lithography and is shelf stable.