Semiconductor device and method for manufacturing the same

Abstract

A region containing a high proportion of crystal components and a region containing a high proportion of amorphous components are formed separately in one oxide semiconductor film. The region containing a high proportion of crystal components is formed so as to serve as a channel formation region and the other region is formed so as to contain a high proportion of amorphous components. It is preferable that an oxide semiconductor film in which a region containing a high proportion of crystal components and a region containing a high proportion of amorphous components are mixed in a self-aligned manner be formed. To separately form the regions which differ in crystallinity in the oxide semiconductor film, first, an oxide semiconductor film containing a high proportion of crystal components is formed and then process for performing amorphization on part of the oxide semiconductor film is conducted.

What is claimed is: 
     
         1 . A method for manufacturing a semiconductor device, comprising the steps of:
 forming an oxide semiconductor layer comprising a crystal region;   selectively introducing an element to the oxide semiconductor layer to form a first region to which the element is introduced and a second region to which the element is introduced in the oxide semiconductor layer so that a third region to which the element is not introduced is positioned between the first region and the second region; and   forming a source electrode layer and a drain electrode layer over the first region and the second region, respectively,   wherein a hydrogen concentration of each of the first region and the second region is higher than a hydrogen concentration of the third region, and   wherein a crystallinity of each of the first region and the second region is lower than a crystallinity of the third region.   
     
     
         2 . The method for manufacturing a semiconductor device according to  claim 1 ,
 wherein the element is introduced by any method selected from the group consisting of a plasma treatment, an ion doping method, and an ion implantation method.   
     
     
         3 . The method for manufacturing a semiconductor device according to  claim 1 ,
 wherein the element is selected from the group consisting of argon, oxygen, phosphorus, arsenic, antimony, boron, aluminum, tungsten, molybdenum, indium, gallium, fluorine, chlorine, titanium, and zinc.   
     
     
         4 . The method for manufacturing a semiconductor device according to  claim 1 ,
 wherein a density of the third region is higher than 6.0 g/cm 3  and lower than 6.375 g/cm 3 .