Disclosed is a method of fabricating a semiconductor device, in which an interlayer insulating film having a low dielectric constant is formed by coating a wiring, and either a via hole or a contact hole is formed in the interlayer insulating film. The method of fabricating a semiconductor device having the interlayer insulating film 25 formed on the film-formed substrate 21 with the exposed wiring 23, comprises the step of converting a silicon compound containing only the Si, O, C and H into a plasma gas as a film-forming gas to react the plasma gas, thus forming the block insulating film 24 containing silicon (Si), oxygen (O), carbon (C) and hydrogen (H) between the wiring 23 and the interlayer insulating film 25.