Patent ID: 7351643

Claim:
A method of fabricating a semiconductor device having a silicon dioxide film disposed at an upper layer of the semiconductor device and a BPSG film disposed below the silicon dioxide film, the BPSG film having gate electrodes therein, and no silicon nitride film being disposed on top and side surfaces of the gate electrodes and no silicon nitride film being disposed above the gate electrodes, the method including formation of a contact hole between adjacent gate electrodes, the contact hole formation method comprising the steps of: etching the silicon dioxide film by a mixed gas of CF 4 , O 2 and Ar at a substrate temperature of at least 40° C. using a resist mask layer for forming the contact hole, and etching the BPSG film by over-etching of the silicon dioxide film so that a W-like shape is formed in the BPSG film; and subsequently etching the BPSG film by a mixed gas of C 4 F 8 , CH 2 F 2 and Ar without including CO gas and O 2 gas so that the contact hole between the adjacent gate electrodes has a forward tapered shape with a tapered angle of less than 90 degree.