PURPOSE: To prevent the generation of aluminum fluorides and Teflon deposited materials in a dry etching process for an insulating film on an aluminum wiring layer and to reduce a defective contact.

CONSTITUTION: A silicon oxide film 4 adhered on an aluminum wiring layer 3 on a silicon substrate 1 is subjected to dry etching with fluorine gas and thereafter irradiated with plasma using oxygen and Teflon deposited materials 6 are removed. Then, while substrate 1 is heated, the substrate is subjected to overetching with bromine gas or chlorine gas, whereby aluminum fluorides are prevented from being produced as deposited materials. Lastly, they are irradiated with plasma using nitrogen and residues of bromine atoms and chlorine atoms, which cause corrosion of the aluminum wiring layer, are removed.