PURPOSE: To prevent short-circuiting between an aluminum electrode and wiring by leaving no etching residue at all in patterning Al using a positive resist.

CONSTITUTION: An insulating layer 2 made of SiO2 is formed on a semiconductor substrate 1, and an Al layer 3 to be formed as the wiring layer of the first layer is formed on the layer 2. On the layer 3, a protective film 9 of a silicone resin is formed on the layer 3, and moreover on the film 9, a positive resist 4 is formed. This resist 4 is exposed and developed, and the silicone resin 9 is etched with a fluorine type gas by using the obtained positive resist 4 mask. Then, the Al layer 3 is etched by changing over said gas to a chlorine type gas, and the wiring Al layers 3, 3' separated from each other are formed.