To protect a laminated wiring against undercuts and side etching by a method wherein a laminated structure composed of a high-melting metal layer and an Al metal is plasma-etched with etching gas which comprises gas composed of, at least, H and O and gas capable of generating chlorine chemical species.

An insulating film 1 of SiO2 or the like, a Ti close contact layer 2, a TiN barrier metal layer 3, a high-melting metal layer 4 of W formed through a blanket CVD method, an Al metal layer 5 formed by sputtering, and an anti-reflection layer 6 of TiON are successively formed in this sequence on a semiconductor substrate of Si or the like. Radical reaction where Cl+ dissociated and produced from Cl2 and BCl3 by an ECR discharge is made to serve as main etching species is assisted by ions such as Clx+, BClx+, and O+, and etching is anisotropically advanced. An Al/W laminated wiring is protected against side etching when it is etched through a one-step etching method where BCl3/Cl2/H2O/mixed gas is used.