FORMATION OF POLYCIDE GATE

PROBLEM TO BE SOLVED: To provide a method of forming a polycide gate which makes a good profile possess to the gate and does not make etching residues exist on the gate. SOLUTION: A method of forming a polycide gate comprises a step for forming in order a gate insulating film, a polysilicon film and a silicide film on a semiconductor substrate, a step for forming a mask layer on the above silicide film and a step for etching the above silicide and polysilicon films using the mixed gas of chlorine gas (Cl2 gas) with oxygen gas (O2 gas) and the above oxygen gas is added to the silicide and polysilicon films at a rate of 10 to 30% of the whole etching gas, whereby the phenomenon of an infringement of the sidewalls of a polycide pattern is prevented from being generated and the problem of residues is solved by applying properly bias power. Moreover, the infringement of the sidewalls of the pattern and the problem of the residues can be simultaneously solved by adding a prescribed amount only of F or C-F gas to the Cl2 /O2 gases and a loss of a gate oxide film can be also inhibited.