US Patent 9799773 Transistor and semiconductor device

A transistor which withstands a high voltage and controls large electric power can be provided. A transistor is provided which includes a gate electrode, a gate insulating layer over the gate electrode, an oxide semiconductor layer which is over the gate insulating layer and overlaps with the gate electrode, and a source electrode and a drain electrode which are in contact with the oxide semiconductor layer and whose end portions overlap with the gate electrode. The gate insulating layer includes a first region overlapping with the end portion of the drain electrode and a second region adjacent to the first region. The first region has smaller capacitance than the second region.