In a process of fabrication of a semiconductor device having a relatively deep contact hole and a relatively shallow contact hole; a lower interlayer insulating layer is formed on a semiconductor substrate, and then subjected to heat treatment to flow; an upper interlayer insulating film is then formed on the lower interlayer insulating film, and is then subjected to heat treatment to flow; a non-flowing film which does not flow is then formed in the area where the shallow contact hole will be formed; and the deep and the shallow holes are then formed through the upper interlayer insulating film and the non-flowing film and heat treatment is conducted to cause flow of the upper interlayer insulating film whereby the flow of the upper interlayer insulating layer occurs except at the area covered by the non-flowing film. The deep and the shallow contact holes are then filled with metal by selective CVD; and an interconnection is then formed to have contact with the metal filling the contact holes.