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 semiconductor layer;   a first electrode and a second electrode electrically connected to the semiconductor layer;   a first gate insulating layer and a second gate insulating layer with the semiconductor layer therebetween;   a first gate electrode overlapping with the first electrode, the semiconductor layer, and the second electrode with the first gate insulating layer located between the first gate electrode and the first electrode, the first gate electrode and the semiconductor layer, and the first gate electrode and the second electrode; and   a second gate electrode overlapping with the semiconductor layer and the first electrode with the second gate insulating layer located between the second gate electrode and the semiconductor layer, and the second gate electrode and the first electrode,   wherein the second gate electrode does not overlap with the second electrode, and   wherein a length of the first gate electrode is longer than a length of the semiconductor layer in a channel length direction.   
     
     
         2 . The semiconductor device according to  claim 1 ,
 wherein the first electrode is a drain electrode, and   wherein the second electrode is a source electrode.   
     
     
         3 . The semiconductor device according to  claim 1 ,
 wherein the first electrode is a source electrode, and   wherein the second electrode is a drain electrode.   
     
     
         4 . The semiconductor device according to  claim 3 , wherein the second gate electrode is electrically connected to receive a potential lower than a potential applied to the source electrode. 
     
     
         5 . The semiconductor device according to  claim 1 ,
 wherein the semiconductor layer has an island shape,   wherein one of the first electrode and the second electrode has a ring shape and an opening of the ring shape overlaps with the semiconductor layer, and   wherein the other of the first electrode and the second electrode is in the opening.   
     
     
         6 . The semiconductor device according to  claim 1 , wherein the semiconductor layer includes an oxide semiconductor. 
     
     
         7 . The semiconductor device according to  claim 6 , further comprising an oxide layer on an opposite side of the semiconductor layer with the second gate insulating layer therebetween,
 wherein the oxide layer contains oxygen at a higher proportion than oxygen in a stoichiometric composition.   
     
     
         8 . The semiconductor device according to  claim 6 , further comprising:
 a first oxide layer between the semiconductor layer and the second gate insulating layer; and   a second oxide layer between the semiconductor layer and the first gate insulating layer,   wherein the first oxide layer and the second oxide layer each contain one or more of metal elements contained in the semiconductor layer.   
     
     
         9 . A semiconductor device comprising;
 a semiconductor layer;   a first electrode and a second electrode electrically connected to the semiconductor layer;   a first gate insulating layer and a second gate insulating layer with the semiconductor layer therebetween;   a first gate electrode overlapping with the first electrode, the semiconductor layer, and the second electrode with the first gate insulating layer located between the first gate electrode and the first electrode, the first gate electrode and the semiconductor layer, and the first gate electrode and the second electrode;   a second gate electrode overlapping with the semiconductor layer and the first electrode with the second gate insulating layer located between the second gate electrode and the semiconductor layer, the second gate electrode and the first electrode; and   a third gate electrode overlapping with the second electrode with the second gate insulating layer therebetween,   wherein the second gate electrode does not overlap with the second electrode.   
     
     
         10 . The semiconductor device according to  claim 9 ,
 wherein the second gate electrode and the third gate electrode are apart from each other in a region overlapping with the semiconductor layer.   
     
     
         11 . The semiconductor device according to  claim 9 , further comprising an insulating layer between the second gate electrode and the third gate electrode. 
     
     
         12 . The semiconductor device according to  claim 11 , wherein the second gate electrode overlaps with the third gate electrode. 
     
     
         13 . The semiconductor device according to  claim 9 , wherein the first gate electrode is electrically connected to the third gate electrode. 
     
     
         14 . The semiconductor device according to  claim 9 ,
 wherein the first electrode is a drain electrode, and   wherein the second electrode is a source electrode.   
     
     
         15 . The semiconductor device according to  claim 9 ,
 wherein the first electrode is a source electrode, and   wherein the second electrode is a drain electrode.   
     
     
         16 . The semiconductor device according to  claim 15 , wherein the second gate electrode is electrically connected to receive a potential lower than a potential applied to the source electrode. 
     
     
         17 . The semiconductor device according to  claim 9 ,
 wherein the semiconductor layer has an island shape,   wherein one of the first electrode and the second electrode has a ring shape and an opening of the ring shape overlaps with the semiconductor layer, and   wherein the other of the first electrode and the second electrode is in the opening.   
     
     
         18 . The semiconductor device according to  claim 9 , wherein the semiconductor layer includes an oxide semiconductor. 
     
     
         19 . The semiconductor device according to  claim 18 , further comprising an oxide layer on an opposite side of the semiconductor layer with the second gate insulating layer therebetween,
 wherein the oxide layer contains oxygen at a higher proportion than oxygen in a stoichiometric composition.   
     
     
         20 . The semiconductor device according to  claim 18 , further comprising:
 a first oxide layer between the semiconductor layer and the second gate insulating layer; and   a second oxide layer between the semiconductor layer and the first gate insulating layer,   wherein the first oxide layer and the second oxide layer each contain one or more of metal elements contained in the semiconductor layer.