PURPOSE: To obtain a thin polycrystalline Si film transistor having preferable characteristics by forming source and drain electrodes, plasma oxidizing the surfaces, and removing Si oxide with a solution containing hydrofluoric acid formed by the plastic oxidation.
CONSTITUTION: After source and drain electrodes 4 and 5 are formed, the surfaces are plasma oxidized. Then, the surfaces are etched with a solution containing hydrofluoric acid. According to this method, the surface of a polycrystalline Si semiconductor film 2 can be oxidized at a low temperature. Thus, it can prevent the invasion of undesired impurity, and since the oxide of the Si produced at that time can be readily removed with the solution containing the hydrofluoric acid, the surface including aluminum which is subjected to solid solution on the polycrystalline Si surface layer can be cleaned. The source and drain electrode patterns are simultaneously oxidized, but the produce aluminum oxide is hardly dissolved in the hydrofluoric acid. Accordingly, only the surface of the Si film can be selectively etched. As a consequence, the Si surface can be cleaned without affecting adverse influence to the other, thereby obtaining preferable characteristics.
SUNAHARA KAZUO
TANABE HIDEO
EZAWA MASAYOSHI
MISUMI AKIRA
