Semiconductor device and manufacturing method thereof

Abstract

An object is to provide a semiconductor device of which a manufacturing process is not complicated and by which cost can be suppressed, by forming a thin film transistor using an oxide semiconductor film typified by zinc oxide, and a manufacturing method thereof. For the semiconductor device, a gate electrode is formed over a substrate; a gate insulating film is formed covering the gate electrode; an oxide semiconductor film is formed over the gate insulating film; and a first conductive film and a second conductive film are formed over the oxide semiconductor film. The oxide semiconductor film has at least a crystallized region in a channel region.

1 . (canceled) 
     
     
         2 . A method for manufacturing a semiconductor device, comprising:
 forming a first conductive film that serves as a first gate electrode;   forming a first insulating film over the first conductive film;   forming an oxide semiconductor film over the first insulating film;   forming a source electrode and a drain electrode by patterning a second conductive film formed over the oxide semiconductor film, whereby a top surface of a first region of the oxide semiconductor film that is located between the source electrode and the drain electrode is etched to have a smaller thickness than a second region of the oxide semiconductor film that is below the source electrode or the drain electrode;   forming a second insulating film over the oxide semiconductor film, the source electrode, and the drain electrode; and   forming a transparent film over the second insulating film by a sputtering method,   wherein the transparent film comprises metal oxide.   
     
     
         3 . The method according to  claim 2 ,
 wherein the oxide semiconductor film includes indium, zinc, and a metal different from indium and zinc.   
     
     
         4 . The method according to  claim 2 ,
 wherein the transparent film is a conductive film.   
     
     
         5 . The method according to  claim 2 , further comprising:
 performing a heat treatment on the oxide semiconductor film.   
     
     
         6 . The method according to  claim 2 ,
 wherein the second insulating film is in contact with the oxide semiconductor film and the transparent film.   
     
     
         7 . The method according to  claim 2 ,
 wherein the transparent film includes indium.   
     
     
         8 . The method according to  claim 2 ,
 wherein the transparent film includes zinc.   
     
     
         9 . A method for manufacturing a semiconductor device, comprising:
 forming a first conductive film that serves as a first gate electrode;   forming a first insulating film over the first conductive film;   forming an oxide semiconductor film over the first insulating film;   forming a source electrode and a drain electrode by patterning a second conductive film formed over the oxide semiconductor film, whereby a top surface of a first region of the oxide semiconductor film that is located between the source electrode and the drain electrode is etched to have a smaller thickness than a second region of the oxide semiconductor film that is below the source electrode or the drain electrode;   forming a second insulating film over the oxide semiconductor film, the source electrode, and the drain electrode; and   forming a transparent film over the second insulating film by a sputtering method,   wherein the transparent film comprises metal oxide, and   wherein the second insulating film is an oxide insulating film.   
     
     
         10 . The method according to  claim 9 ,
 wherein the oxide semiconductor film includes indium, zinc, and a metal different from indium and zinc.   
     
     
         11 . The method according to  claim 9 ,
 wherein the transparent film is a conductive film.   
     
     
         12 . The method according to  claim 9 , further comprising:
 performing a heat treatment on the oxide semiconductor film.   
     
     
         13 . The method according to  claim 9 ,
 wherein the second insulating film is in contact with the oxide semiconductor film and the transparent film.   
     
     
         14 . The method according to  claim 9 ,
 wherein the transparent film includes indium.   
     
     
         15 . The method according to  claim 9 ,
 wherein the transparent film includes zinc.