Thin film transistor, semiconductor device, and method for manufacturing the same

Abstract

A semiconductor element is operated without being affected even when the substrate is largely affected by heat shrink such as a large substrate. Furthermore, a thin film semiconductor circuit and a thin film semiconductor device each having the semiconductor element. Also, a semiconductor element is operated without being affected even if there is slight mask deviation. In view of them, a plurality of gate electrodes formed so as to overlap a lower concentration impurity region of a semiconductor layer than drain regions on a drain region side. Also, source regions and the drain regions corresponding to the respective gate electrodes are formed so that current flows in opposite directions each other through channel regions corresponding to the gate electrodes. Further, the number of the channel regions in which a current flows in a first direction is equal to the number of the channel regions in which a current flows in a direction opposite to the first direction.

1 . (canceled) 
     
     
         2 . An electroluminescent device comprising:
 a pixel over a glass substrate, the pixel comprising:
 a base insulating film over and in contact with the glass substrate; 
 a semiconductor layer over the base insulating film, the semiconductor layer having a rectangular shape and comprising a first doped region, a first channel formation region, a second doped region, a second channel formation region, and a third doped region in this order along a longitudinal direction of the semiconductor layer; 
 a gate insulating film over the semiconductor layer; 
 a first wiring over the gate insulating film and overlapping with the first channel formation region and the second channel formation region; 
 an interlayer insulating film over the first wiring; 
 a second wiring over the interlayer insulating film, the second wiring passing the interlayer insulating film and being in direct contact to the second doped region; 
 a third wiring over the interlayer insulating film, the second wiring extending a direction parallel to the longitudinal direction, passing the interlayer insulating film, and being in direct contact to the first doped region and the second doped region; 
 a pixel electrode over the interlayer insulating film; 
 a bank covering an edge portion of the pixel electrode; 
 an electroluminescent layer over the pixel electrode and the bank; and 
 a second electrode over the electroluminescent layer, 
   wherein the pixel electrode is transparent so that light emitted from the electroluminescent layer is extracted through the glass substrate.   
     
     
         3 . The electroluminescent device according to  claim 2 ,
 wherein the semiconductor layer is configured so that a current direction in the first channel formation region is opposite to that in the second channel formation region.   
     
     
         4 . The electroluminescent device according to  claim 2 ,
 wherein the first doped region and the third doped region are doped with the same impurity.   
     
     
         5 . The electroluminescent device according to  claim 2 ,
 wherein the first doped region, the second doped region, and the third doped region are doped with the same impurity.   
     
     
         6 . The electroluminescent device according to  claim 4 ,
 wherein the impurity doped in the first doped region and the third doped region is a p-type impurity.   
     
     
         7 . The electroluminescent device according to  claim 5 ,
 wherein the impurity doped in the first doped region, the second doped region, and the third doped region is a p-type impurity.   
     
     
         8 . The electroluminescent device according to  claim 2 ,
 wherein the bank is a silicon-oxide layer.   
     
     
         9 . The electroluminescent device according to  claim 2 ,
 wherein the first wiring extends in a direction parallel to the longitudinal direction.   
     
     
         10 . An electronic device comprising the electroluminescent device according to  claim 2 . 
     
     
         11 . An electroluminescent device comprising:
 a pixel over a glass substrate, the pixel comprising:
 a base insulating film over and in contact with the glass substrate; and 
 a first transistor and a second transistor over the base insulating film, 
   wherein the first transistor comprises a first semiconductor layer and a plurality of gate electrodes over the first semiconductor layer, and   wherein the second transistor comprises:
 a second semiconductor layer over the base insulating film, the second semiconductor layer having a rectangular shape and comprising a first doped region, a first channel formation region, a second doped region, a second channel formation region, and a third doped region in this order along a longitudinal direction of the second semiconductor layer; 
 a gate insulating film over the second semiconductor layer; 
 a first wiring over the gate insulating film and overlapping with the first channel formation region and the second channel formation region; 
 an interlayer insulating film over the first wiring; 
 a second wiring over the interlayer insulating film, the second wiring passing the interlayer insulating film and being in direct contact to the second doped region; 
 a third wiring over the interlayer insulating film, the second wiring extending a direction parallel to the longitudinal direction, passing the interlayer insulating film, and being in direct contact to the first doped region and the second doped region; 
 a pixel electrode over the interlayer insulating film; 
 a bank covering an edge portion of the pixel electrode; 
 an electroluminescent layer over the pixel electrode and the bank; and 
 a second electrode over the electroluminescent layer, and 
   wherein the pixel electrode is transparent so that light emitted from the electroluminescent layer is extracted through the glass substrate.   
     
     
         12 . The electroluminescent device according to  claim 11 ,
 wherein the second semiconductor layer is configured so that a current direction in the first channel formation region is opposite to that in the second channel formation region.   
     
     
         13 . The electroluminescent device according to  claim 11 ,
 wherein the first doped region and the third doped region are doped with the same impurity.   
     
     
         14 . The electroluminescent device according to  claim 11 ,
 wherein the first doped region, the second doped region, and the third doped region are doped with the same impurity.   
     
     
         15 . The electroluminescent device according to  claim 13 ,
 wherein the impurity doped in the first doped region and the third doped region is a p-type impurity.   
     
     
         16 . The electroluminescent device according to  claim 14 ,
 wherein the impurity doped in the first doped region, the second doped region, and the third doped region is a p-type impurity.   
     
     
         17 . The electroluminescent device according to  claim 11 ,
 wherein the bank is a silicon-oxide layer.   
     
     
         18 . The electroluminescent device according to  claim 11 ,
 wherein the first wiring extends in a direction parallel to the longitudinal direction.   
     
     
         19 . An electronic device comprising the electroluminescent device according to  claim 11 .