Semiconductor device

Abstract

To provide a semiconductor device in which a large current can flow. To provide a semiconductor device which can be driven stably at a high driving voltage. The semiconductor device includes a semiconductor layer, a first electrode and a second electrode electrically connected to the semiconductor layer and apart from each other in a region overlapping with the semiconductor layer, a first gate electrode and a second gate electrode with the semiconductor layer therebetween, a first gate insulating layer between the semiconductor layer and the first gate electrode, and a second gate insulating layer between the semiconductor layer and the second gate electrode. The first gate electrode overlaps with part of the first electrode, the semiconductor layer, and part of the second electrode. The second gate electrode overlaps with the semiconductor layer and part of the first electrode, and does not overlap with the second electrode.

1 . A semiconductor device comprising:
 a second gate electrode over a substrate;   a semiconductor layer over the second gate electrode;   a source electrode and a drain electrode, each over and in contact with the semiconductor layer; and   a first gate electrode over the source electrode and the drain electrode,   wherein the first gate electrode overlaps both of the source electrode and the drain electrode,   wherein, in a channel length direction, both ends of the semiconductor layer extend beyond both ends of the first gate electrode, and   wherein, in the channel length direction, one end of the second gate electrode extends beyond one of the both ends of the semiconductor layer.   
     
     
         2 . The semiconductor device according to  claim 1 , wherein a gate insulating layer is provided between the second gate electrode and the semiconductor layer, and between the semiconductor layer and the first gate electrode. 
     
     
         3 . The semiconductor device according to  claim 1 , wherein the semiconductor layer is an oxide semiconductor layer. 
     
     
         4 . A semiconductor device comprising:
 a second gate electrode over a substrate;   a semiconductor layer over the second gate electrode;   a source electrode and a drain electrode, each over and in contact with the semiconductor layer; and   a first gate electrode over the source electrode and the drain electrode,   wherein the first gate electrode overlaps both of the source electrode and the drain electrode,   wherein, in a channel length direction, both ends of the semiconductor layer extend beyond both ends of the first gate electrode,   wherein, in the channel length direction, one end of the second gate electrode extends beyond one of the both ends of the semiconductor layer, and   wherein each of the first gate electrode, the second gate electrode, the source electrode and the drain electrode extends in a channel width direction.   
     
     
         5 . The semiconductor device according to  claim 4 , wherein a gate insulating layer is provided between the second gate electrode and the semiconductor layer, and between the semiconductor layer and the first gate electrode. 
     
     
         6 . The semiconductor device according to  claim 4 , wherein the semiconductor layer is an oxide semiconductor layer.