A method for anisotropic etching of a layer of a silicon-based material, using an SF.sub.6 gas, a versatile etching gas, is proposed. Sulfur (S) is used as a sidewall protection substance. This sulfur is not supplied into an etching reaction system on discharge dissociation of the etching gas, but is supplied by being sublimed off on heating from the inner wall surface of the etching chamber on which it is previously grown from a gaseous phase. Specifically, the S.sub.2 F.sub.2 gas is introduced while a predetermined region of the inner wall surface of the etching chamber is cooled, and preliminary discharge is carried out to deposit sulfur on the region. A SF.sub.6 containing etching gas is introduced into the chamber and the above mentioned region is heated for subliming S and simultaneously etching the layer of the silicon-based material. With this method, there is no necessity of using a specific etching gas capable of yielding free S in the plasma under discharge dissociating conditions. The present invention has an important significance as post-CFC (chlorofluorocarbon) gas measures. After end of etching, sulfur may be easily sublimed off by heating the wafer without the risk of pollution by particles.