A semiconductor device includes a substrate and an oxide semiconductor TFT including an oxide semiconductor layer supported by the substrate and having a multilayer structure including a protective oxide semiconductor layer and a channel oxide semiconductor layer disposed closer to the substrate than the protective oxide semiconductor layer, an upper insulating layer on the oxide semiconductor layer, an upper gate electrode disposed on the upper insulating layer, an interlayer insulating layer covering the oxide semiconductor layer and the upper gate electrode, and first and second electrodes electrically connected to the oxide semiconductor layer, wherein a first opening extends through at least the interlayer insulating layer and the protective oxide semiconductor layer, and exposes a portion of the channel oxide semiconductor layer, and the first electrode is disposed on the interlayer insulating layer and within the first opening, and is in direct contact with, within the first opening, the portion.