Patent ID: 8642402

Claim:
A method for producing a thin film transistor comprising the steps of: a film-forming step in which an amorphous oxide film is formed as a channel layer; a patterning step in which said amorphous oxide film is patterned by etching; and a crystallization step in which said amorphous oxide film which is patterned in the patterning step is crystallized, resulting in the amorphous oxide film being converted to a crystalline oxide semiconductor film, wherein said crystallized crystalline oxide semiconductor film is provides a channel layer; said crystalline oxide semiconductor film contains In and a positive divalent element; said positive divalent element is one or more elements selected from Zn, Mg, Cu, Co, Ni and Ca; and an atomic ratio of the In [In] and the positive divalent element [X] by the formula [X]/([X]+[In]) is such that 0.0001≦[X]/([X]+[In])≦0.5.