PURPOSE: To eliminate a palladium treatment process from an electrode formation process, to make it possible to shorten the process of manufacture, and to cut down the cost by a method wherein washing and conveying operations are conducted in the washing water in which dissolved oxygen is removed by inert gas and the environment in which oxygen is removed by inert gas.

CONSTITUTION: A silicon oxide layer 2 is laminated on an N-type silicon substrate 1 by a thermal oxidization method, an aluminum A alloy layer 3 is laminated thereon by a vacuum-deposition method, and a silicon layer 4 is covered thereon using a CVD method. Then, an expected region of electrode formation of 30×30μm is etched by a photolithography method. This substrate is degreased and after Al has been etched by a sulfuric solution, the substrate is washed by the washing water purged by the nitrogen-gas-replaced non-oxygen atmosphere and nitrogen gas. Lastly, the substrate 15 carried in a non-oxygen atmosphere, a nickel-phosphorus layer 5 is plated by a electroless plating solution under the prescribed plating condition, and the electrode of a semiconductor device is completed. In order to prevent Al from oxidation in the air of an aqueous solution, a plating treatment and a conveying operation are conducted in the water and the environment wherein oxygen is removed to the never generating no Al oxidation after the natural oxide film of Al is removed.