PURPOSE: To safely carry out etching with excellent etching rate, selectivity and anisotropy by using C2Br2F4 or C2BrF5 or those added with a specified amt. of SF6 as the gaseous reactant for dry etching.

CONSTITUTION: A gaseous reactant is introduced into an evacuated chamber, and the surface of a sample set in the chamber is etched through plasma or reactive ion. In this dry etching method, C2Br2F4 or C2BrF5 or those gases added with 50vol.% SF6 are used as the gaseous reactant. The sample temp. is preferably kept at ≤-20°C when the gas contg. ≤50vol.% SF6 is used. The gaseous reactant is excellent in the anisotropy, etching rate and selective ratio, and minute and precise etching is performed. Furthermore, the contamination of the chamber is reduced, clean treatment is realized, and the reactant is advantageous from the standpoint of safety since it does not contain chlorine, etc.