Abstract: A method for forming an element isolation structure of a semiconductor device, includes: a trench forming step of forming a trench on a semiconductor substrate; and a laminating step of forming alternately multilayered film in the trench by sequentially and alternately laminating a plurality of first insulating films that apply tensile stress to the semiconductor substrate and a plurality of second insulating films that apply compression stress to the semiconductor substrate so that the trench is filled with the alternately multilayered film.

Abstract: A method of forming an insulating film according to the present invention reacts a nitrogen containing gas with a compound composed of silicon and chlorine under the condition that the gas flow ratio of the compound to the nitrogen containing gas is lower than {fraction (1/30)} to form a silicon nitride film. In the present invention, by forming the silicon nitride film at the gas flow ratio lower than {fraction (1/30)}, an insulating film having this silicon nitride film is improved in electric insulating property, so that a smaller leak current flows therethrough.