Provided is a top gate thin film transistor, including on a substrate: a source electrode layer; a drain electrode layer; an oxide semiconductor layer; a gate insulating layer; a gate electrode layer including an amorphous oxide semiconductor containing at least one kind of element selected from among In, Ga, Zn, and Sn; and a protective layer containing hydrogen, in which: the gate insulating layer is formed on a channel region of the oxide semiconductor layer; the gate electrode layer is formed on the gate insulating layer; and the protective layer is formed on the gate electrode layer.