PURPOSE: To protect the development of corrosion of a semiconductor device even when the device is exposed to the atmosphere after ashing is applied to the device by carrying out dry etching on a single or multi-circuit layer containing aluminum alloy prepared on a wafer, followed by ashing the resist under a particular high temperature range.

CONSTITUTION: Single or multi-circuit layers containing at least aluminum alloy 304 are prepared on a wafer, followed by ashing the resist 305 under a high temperature greater than 200°C. As a result, chloride 306 such as etching reactive product that is adherent to the side wall of the circuit layer or resist 305 is removed by evaporation due to the processing under high temperature. When the treatment is done under a temperature higher than 200°C, the effect of removing chloride is sufficient enough to stop corrosion even when the semiconductor device is exposed to the atmosphere.