| abstract |
A semiconductor device includes a first gate electrode; a gate insulating layer covering the first gate electrode; an oxide semiconductor layer that overlaps with the first gate electrode; oxide semiconductor layers having high carrier density covering end portions of the oxide semiconductor layer; a source electrode and a drain electrode in contact with the oxide semiconductor layers having high carrier density; an insulating layer covering the source electrode, the drain electrode, and the oxide semiconductor layer; and a second gate electrode that is in contact with the insulating layer. Each of the oxide semiconductor layers is in contact with part of each of an upper surface, a lower surface, and a side surface of one of the end portions of the oxide semiconductor layer and part of an upper surface of the gate insulating layer. |