A method is disclosed for the formation of a planarizing coating film on the surface of a substrate having a stepped level difference under processing for the manufacture of semiconductor devices. The inventive method capable of giving a planarizing coating film of excellent planarity and good adhesion to the substrate surface comprises the steps of: (a) coating the substrate surface with a coating solution containing, as a film-forming solute uniformly dissolved in an ,organic solvent, a nitrogen-containing organic compound such as benzoguanamine and melamine having, in a molecule, at least two amino and/or imino groups each substituted for the nitrogen-bonded hydrogen atom by a hydroxyalkyl group or an alkoxyalkyl group to form a coating layer; (b) drying the coating layer by evaporating the organic solvent to form a dried coating layer; and (c) subjecting the dried coating layer to a baking treatment at a temperature in the range from 150 to 250.degree. C.