US Patent 8053836 Oxide semiconductor thin-film transistor

An oxide semiconductor thin-film transistor, comprising: a source electrode and a drain electrode formed on a substrate; a composite semiconductor active layer formed between the source electrode and the drain electrode; a gate dielectric layer formed on the source electrode, the composite semiconductor active layer and the drain electrode; and a gate electrode formed on the gate dielectric layer and corresponding to the composite semiconductor active layer; wherein the composite semiconductor active layer comprises a low carrier-concentration first oxide semiconductor layer and a high carrier-concentration second oxide semiconductor layer.