Semiconductor device and method for manufacturing the same

Abstract

Many of the physical properties of a silicon semiconductor have already been understood, whereas many of the physical properties of an oxide semiconductor have been still unclear. In particular, an adverse effect of an impurity on an oxide semiconductor has been still unclear. In view of the above, a structure is disclosed in which an impurity that influences electrical characteristics of a semiconductor device including an oxide semiconductor layer is prevented or is eliminated. A semiconductor device which includes a gate electrode, an oxide semiconductor layer, and a gate insulating layer provided between the gate electrode and the oxide semiconductor layer and in which the nitrogen concentration in the oxide semiconductor layer is 1×1020 atoms/cm3 or less is provided.

1 . An electroluminescence display device comprising:
 an island-shaped oxide semiconductor layer comprising In, Ga, and Zn;   a silicon oxide film over the oxide semiconductor layer;   a first electrode over the oxide semiconductor layer;   a second electrode over the oxide semiconductor layer; and   a third electrode overlapping with the oxide semiconductor layer,   wherein the silicon oxide film is in contact with the oxide semiconductor layer,   wherein the first electrode is configured to be one of a source and a drain,   wherein the second electrode is configured to be the other of the source and the drain,   wherein the one of the first electrode and the second electrode is electrically connected with one electrode of a light-emitting device, and   wherein a nitrogen concentration in the oxide semiconductor layer is 1×10 19  atoms/cm 3  or less.   
     
     
         2 . The electroluminescence display device according to  claim 1 ,
 wherein a transistor comprises the oxide semiconductor layer, and   wherein the transistor comprises an offset structure.   
     
     
         3 . The electroluminescence display device according to  claim 1 ,
 wherein the silicon oxide film comprises a region in contact with a side surface of the oxide semiconductor layer.   
     
     
         4 . The electroluminescence display device according to  claim 2 ,
 wherein the silicon oxide film comprises a region in contact with a side surface of the oxide semiconductor layer.   
     
     
         5 . An electroluminescence display device comprising:
 an island-shaped oxide semiconductor layer comprising In, Ga, and Zn;   a silicon oxide film over the oxide semiconductor layer;   a first electrode over the oxide semiconductor layer;   a second electrode over the oxide semiconductor layer; and   a third electrode overlapping with the oxide semiconductor layer,   wherein the silicon oxide film is in contact with the oxide semiconductor layer,   wherein the first electrode is configured to be one of a source and a drain,   wherein the second electrode is configured to be the other of the source and the drain,   wherein the one of the first electrode and the second electrode is electrically connected with one electrode of a light-emitting device,   wherein a nitrogen concentration in the oxide semiconductor layer is 1×10 19  atoms/cm 3  or less, and   wherein a thickness of the oxide semiconductor layer is 20 to 80 nm.   
     
     
         6 . The electroluminescence display device according to  claim 5 ,
 wherein a transistor comprises the oxide semiconductor layer, and   wherein the transistor comprises an offset structure.   
     
     
         7 . The electroluminescence display device according to  claim 5 ,
 wherein the silicon oxide film comprises a region in contact with a side surface of the oxide semiconductor layer.   
     
     
         8 . The electroluminescence display device according to  claim 6 ,
 wherein the silicon oxide film comprises a region in contact with a side surface of the oxide semiconductor layer.   
     
     
         9 . An electroluminescence display device comprising:
 an oxide semiconductor layer;   a silicon oxide film over the oxide semiconductor layer;   a first electrode over the oxide semiconductor layer;   a second electrode over the oxide semiconductor layer; and   a third electrode overlapping with the oxide semiconductor layer,   wherein the silicon oxide film is in contact with the oxide semiconductor layer,   wherein the first electrode is configured to be one of a source and a drain,   wherein the second electrode is configured to be the other of the source and the drain,   wherein the one of the first electrode and the second electrode is electrically connected with one electrode of a light-emitting device, and   wherein a nitrogen concentration in the oxide semiconductor layer is 1×10 19  atoms/cm 3  or less.   
     
     
         10 . The electroluminescence display device according to  claim 9 ,
 wherein a transistor comprises the oxide semiconductor layer, and   wherein the transistor comprises an offset structure.   
     
     
         11 . The electroluminescence display device according to  claim 9 ,
 wherein the silicon oxide film comprises a region in contact with a side surface of the oxide semiconductor layer.   
     
     
         12 . The electroluminescence display device according to  claim 10 ,
 wherein the silicon oxide film comprises a region in contact with a side surface of the oxide semiconductor layer.