a dry etching method using no organic resist mask without involving an increase in the number of necessary processes or wafer surface steps . conventionally , a nitrogen based compound film is formed as a thin anti - reflection film on a gate electrode or aluminum metallization layer . the nitrogen based compound film thus formed can be used as an etching mask for the material layer by using etching gas capable of forming sulfur in a plasma when dissociated by electric discharges . for instance , a w polycide film masked by a tion anti - reflection film patterned into a predetermined shape can be etched by s 2 f 2 / h 2 mixed gas . in this case , a nitrogen dangling bond formed on the surface of the tion anti - reflection film combines with sulfur supplied by s 2 f 2 to form a polythiazyl x coating , which provides the resulting tion anti - reflection film pattern with a sufficient etching resistance to act as an etching mask . this etching process emits no carbon to the etching system , thus improving selectivity for a sio 2 based material layer . the tion anti - reflection film pattern can also be used as an etching mask for an aluminum metallization layer with a view to reducing after - corrosion .