Semiconductor device

Abstract

A decrease in on-state current in a semiconductor device including an oxide semiconductor film is suppressed. A transistor including an oxide semiconductor film, an insulating film which includes oxygen and silicon, a gate electrode adjacent to the oxide semiconductor film, the oxide semiconductor film provided to be in contact with the insulating film and overlap with at least the gate electrode, and a source electrode and a drain electrode electrically connected to the oxide semiconductor film. In the oxide semiconductor film, a first region which is provided to be in contact with the interface with the insulating film and have a thickness less than or equal to 5 nm has a silicon concentration lower than or equal to 1.0 at. %, and a region in the oxide semiconductor film other than the first region has lower silicon concentration than the first region.

1 . (canceled) 
     
     
         2 . A semiconductor device comprising:
 a gate electrode;   an insulating layer over the gate electrode, the insulating layer including silicon;   an oxide semiconductor layer over the insulating layer, the oxide semiconductor layer including a channel formation region;   wherein the oxide semiconductor layer includes:
 a first region in direct contact with the insulating layer; and 
 a second region over the first region, 
   wherein a concentration of silicon in the first region is lower than or equal to 1.0 at. %, and   wherein a concentration of silicon in the second region is lower than the concentration of silicon in the first region.   
     
     
         3 . The semiconductor device according to  claim 2 , wherein the concentration of silicon included in the first region is lower than or equal to 0.1 at. %. 
     
     
         4 . The semiconductor device according to  claim 2 ,
 wherein the insulating layer includes carbon, and   wherein a concentration of carbon in the first region is lower than or equal to 1.0×10 20  atoms/cm 3 .   
     
     
         5 . The semiconductor device according to  claim 2 , wherein the oxide semiconductor layer has crystallinity. 
     
     
         6 . The semiconductor device according to  claim 2 , wherein the oxide semiconductor layer has an amorphous structure. 
     
     
         7 . The semiconductor device according to  claim 6 , wherein the oxide semiconductor layer includes a crystal portion. 
     
     
         8 . A display device comprising the semiconductor device according to  claim 2 , wherein the display device comprises a display element. 
     
     
         9 . An electronic device comprising the semiconductor device according to  claim 2 . 
     
     
         10 . A semiconductor device comprising:
 an oxide semiconductor layer including a channel formation region;   a gate electrode adjacent to the oxide semiconductor layer;   an insulating layer between the gate electrode and the oxide semiconductor layer, the insulating layer including silicon;   wherein the oxide semiconductor layer includes:
 a first region in direct contact with the insulating layer; and 
 a second region, 
   wherein the first region and the second region overlap each other,   wherein a distance between the first region and the gate electrode is smaller than a distance between the second region and the gate electrode,   wherein a concentration of silicon in the first region is lower than or equal to 1.0 at. %, and   wherein a concentration of silicon in the second region is lower than the concentration of silicon in the first region.   
     
     
         11 . The semiconductor device according to  claim 10 , wherein the concentration of silicon included in the first region is lower than or equal to 0.1 at. %. 
     
     
         12 . The semiconductor device according to  claim 10 ,
 wherein the insulating layer includes carbon, and   wherein a concentration of carbon in the first region is lower than or equal to 1.0×10 20  atoms/cm 3 .   
     
     
         13 . The semiconductor device according to  claim 10 , wherein the oxide semiconductor layer has crystallinity. 
     
     
         14 . The semiconductor device according to  claim 10 , wherein the oxide semiconductor layer has an amorphous structure. 
     
     
         15 . The semiconductor device according to  claim 14 , wherein the oxide semiconductor layer includes a crystal portion. 
     
     
         16 . A display device comprising the semiconductor device according to  claim 10 , wherein the display device comprises a display element. 
     
     
         17 . An electronic device comprising the semiconductor device according to  claim 10 .