Semiconductor device and method for producing it

Abstract

Disclosed is a technique of improving the heat resistance of the aluminum gate electrode in bottom-gate-type TFT of which the active layer is made of a crystalline silicon film. A pattern of a laminate of a titanium filmand an aluminum filmis formed on a glass substrateThe pattern is to give a gate electrodeThen, the titanium filmis side-etched. Next, the layered substrate is heated to thereby intentionally form hillocks and whiskers on the surface of the aluminum patternNext, the aluminum patternacting as an anode is subjected to anodic oxidation to form an oxide filmthereon. The anodic oxidation extends to the lower edge of the aluminum patternat which the titanium layer was side-etched. Next, a gate-insulating filmand an amorphous silicon film are formed. A mask is formed over the pattern, which is to give the gate electrode, and then a nickel acetate solution is applied to the layered structure. Thus, nickel is kept in contact with the surface of the structure. Next, this is heated to induce crystal growth in the silicon film from the region contacted with nickel to the masked region. In the bottom-gate-type TFT thus produced, the active layer is made of a crystalline silicon film. In this process, since the anodic oxide film is formed as in FIG.(C), aluminum does neither melt to flow away nor diffuse away. Thus, the heat resistance of the aluminum electrode formed is improved.