Display device and electronic device including thin film transistor including top-gate

A semiconductor device comprising:

• a first conductive layer comprising an opening;
• an oxide semiconductor layer over the first conductive layer;
• a second conductive layer over the oxide semiconductor layer;
• a third conductive layer over the oxide semiconductor layer;
• a first insulating layer over the oxide semiconductor layer;
• and
• a fourth conductive layer over the first insulating layer,
• wherein the oxide semiconductor layer comprises indium, gallium, and zinc,
• wherein the second conductive layer and the third conductive layer comprise the same metal material,
• wherein the fourth conductive layer is configured to serve as a gate electrode,
• wherein the first conductive layer is electrically connected to the oxide semiconductor layer,
• wherein the second conductive layer is electrically connected to the oxide semiconductor layer,
• wherein the third conductive layer is electrically connected to the oxide semiconductor layer,
• wherein the third conductive layer is electrically connected to the first conductive layer, and
• wherein the second conductive layer is in contact with the oxide semiconductor layer in a region overlapping with the opening of the first conductive layer.