Patent ID: 6848454

Claim:
A method of manufacturing a semiconductor device comprising: a first step of depositing a first film and a second film on a conductive layer in this order and etching a desired portion of the second film with a first etching gas until the first film is exposed, the first film being made of one of a silicon nitride film and a silicon nitride oxide film, the second film being made of a silicon oxide film; a second step of removing a reaction product deposited on the first film through the first step with a second etching gas which consists essentially of O 2 to expose the first film; a third step of etching the first film exposed through the second step with a third etching gas until the conductive layer is exposed; and a fourth step of removing a reaction product deposited on the conductive layer through the third step with a fourth etching gas which consists essentially of O 2 thereby forming a concave portion penetrating the first and second films to reach the conductive layer surface.