Method of manufacturing a semiconductor device

A method of fabricating a semiconductor device having a silicon dioxide film disposed at an upper layer of the semiconductor device, a BPSG film disposed below the silicon dioxide film, and a silicon nitride film disposed below the BPSG film but 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 BPSG film having gate electrodes therein, the method including provision of an organic film on the silicon dioxide film and formation of a contact hole between adjacent gate electrodes, the contact hole formation method comprising the steps of:

• forming a mask pattern with a maximum opening of 0.20 μm in a resist mask applied on the organic film;
• etching the silicon dioxide film and the organic film by a mixed gas of CF4, O2 and Ar at a substrate temperature of at least 40° C., and etching the BPSG film by an over-etching of the silicon dioxide film so that a W-like shape is formed in the BPSG film;
• subsequently etching the BPSG film by a mixed gas of C4F8, CH2F2 and Ar without including CO gas and O2 gas so that the contact hole between the adjacent gate electrodes has a forward tapered shape with a tapered angle of 85 degree;
• and
• subsequently etching the silicon nitride film by an over-etching of the BPSG film.