Patent ID: RE40965

Claim:
A method of forming a contact electrode in a semiconductor device, comprising the steps of: providing a semiconductor substrate having a surface; forming a first insulating film on the surface of the semiconductor substrate, the first insulating film comprising a nondoped silicon glass; forming a second insulating film on the first insulating film, the second insulating film comprising a boron phosphor silicate glass; creating a first hole at least in the second insulating film by isotropic anisotropic etching, thereby leaving the surface of the semiconductor substrate covered by at least part of the thickness dimension of the first insulating film, the first hole being created using a gaseous etchant such that the second insulating film is etched at a higher rate than the first insulating film, the etchant containing carbon and fluorine; heating the second insulating film to a reflowing temperature whereby the first hole in the second insulating film is reshaped to flare as it extends away from the first insulating film; creating a second hole in the first insulating film by isotropic anisotropic etching, with use of a second gaseous etchant containing CHF 3 and CF 4 , the first insulating film through the first hole in the second insulating film, thereby exposing a part of the surface of the semiconductor substrate; and forming a contact electrode by filling the first and the second hole with an electroconductive material.