There is provided an oxide semiconductor layer capable of making stable the electric characteristics of a thin-film transistor without requiring an oxidatively-treated layer when depositing a passivation layer or the like in display devices such as organic EL displays depositing and liquid crystal displays. The thin-film transistor structure of the present invention at least having, on a substrate, an oxide semiconductor layer, a source-drain electrode, and a passivation layer in order from the substrate side, wherein the oxide semiconductor layer is a stacked product of a first oxide semiconductor layer and a second oxide semiconductor layer; the first oxide semiconductor layer has a Zn content of 50 atomic % or more as a percentage of all metal elements contained therein, and the first oxide semiconductor layer is formed on the source-drain electrode and passivation layer side; the second oxide semiconductor layer contains at least one element selected from the group consisting of In, Ga, and Zn, and the second oxide semiconductor layer is formed on the substrate side; and the first oxide semiconductor layer is in direct contact both with the source-drain electrode and with the passivation layer.