FILM FORMING METHOD

PROBLEM TO BE SOLVED: To prevent the peeling of a film in a stress concentration part, by coating the side surface of a step-difference part with a part member of the same material as a thin film, before the thin film is formed on the surface of a substrate having the step-difference part, and previously forming the step- difference part in a taper type. SOLUTION: A tapered part 3 is formed on the side surface 2 of a wiring step-difference 1 by using an insulating film. In this case, SOG is spread on a wafer 4 having a nearly vertical step-difference, with a spinner. The spread SOG is concentrated in the corner part of the wiring step-difference 1 by the effect of surface tension. In this state, the wafer 4 is heated, solvent in the SOG is vaporized, and the step-difference part is tapered. An insulating film 5 is deposited on the whole surface of the wafer 4. When the insulating film 5 is formed by a plasma CVD, the film quality and the film thickness approach a flat part due to ion incidence amount increase from plasma, so that sharp change of the deposition film is eliminated and stress concentration is relieved. As to thermal CVD method, film continuity of a boundary part is improved, and stress concentration is relieved.