Patent ID: 7655572

Claim:
A manufacturing method of a semiconductor device comprising a plasma etching step for performing plasma etching of a dielectric film containing Si formed on a substrate to be processed by use of a photoresist as a mask, wherein the plasma etching step performs the plasma etching by use of an etching gas comprising a mixed gas including a C 4 F 4 O gas, O 2 gas, and at least one rare gas selected from the group consisting of Ne, Ar, Kr, and Xe, so as to etch the dielectric film containing Si selectively to the photoresist, and wherein a range of the ratio of a flow rate of the O 2 gas to a flow rate of the C 4 F 4 O gas (flow rate of O 2 gas/flow rate of C 4 F 4 O gas) in the etching gas is from not less than 1 to not more than 1.35.