Patent ID: 8299461

Claim:
A thin film transistor comprising: a substrate; and, on the substrate, an oxide semiconductor film which serves as an active layer and comprises In, Ga, and Zn, a gate electrode, a gate insulating film, a source electrode, and a drain electrode, wherein, when a molar ratio of In, Ga, and Zn in the oxide semiconductor film is expressed as In:Ga:Zn=(2.0−x):x:y, wherein 0.0<x<2.0 and 0.0<y, the distribution of y in the thickness direction of the oxide semiconductor film is such that the oxide semiconductor film has a region in which a value of y is larger than that at a surface of the oxide semiconductor film at a side closer to the substrate and larger than that at a surface of the oxide semiconductor film at a side farther from the substrate.