Etching method

The present invention relates to an etching method. A processing gas constituted of CF, Oand Ar achieving a flow rate ratio of 1 CFflow rate/Oflow rate 1.625 is supplied into a processing chamber of an etching apparatus and the atmosphere pressure is set within a range of 45 mTorr˜50 mTorr. High-frequency power is applied to a lower electrode sustained within a temperature range of 20° C.˜40° C. on which a wafer W is mounted to raise the processing gas to plasma, and using the plasma, a contact hole is formed at an SiOfilm on an SiNx film formed at the wafer W. The use of CFand Omakes it possible to form a contact hole achieving near-perfect verticality at the SiOfilm and also improves the selection ratio of the SiO2 film relative to the SiNx film . CF, which becomes decomposed over a short period of time when released into the atmosphere, does not induce the greenhouse effect.