Semiconductor device

Abstract

A highly reliable semiconductor device which is formed using an oxide semiconductor and has stable electric characteristics is provided. A semiconductor device which includes an amorphous oxide semiconductor layer including a region containing oxygen in a proportion higher than that in the stoichiometric composition, and an aluminum oxide film provided over the amorphous oxide semiconductor layer is provided. The amorphous oxide semiconductor layer is formed as follows: oxygen implantation treatment is performed on a crystalline or amorphous oxide semiconductor layer which has been subjected to dehydration or dehydrogenation treatment, and then thermal treatment is performed on the oxide semiconductor layer provided with an aluminum oxide film at a temperature lower than or equal to 450° C.

1 . (canceled) 
     
     
         2 . A method for manufacturing a transistor, the method comprising the steps of:
 forming an oxide semiconductor layer over a substrate, the oxide semiconductor layer comprising indium, gallium, and zinc and including a crystalline region; and   increasing the crystalline region.   
     
     
         3 . The method according to  claim 2 ,
 wherein the increase in the crystalline region is performed by heating the oxide semiconductor layer at a temperature equal to or higher than 250° C. and equal to or lower than 700° C.   
     
     
         4 . The method according to  claim 2 , further comprising:
 adding oxygen to the oxide semiconductor layer.   
     
     
         5 . The method according to  claim 2 ,
 wherein the formation of the oxide semiconductor layer is performed while heating the substrate at a temperature equal to or higher than 150° C. and equal to or lower than 450° C.   
     
     
         6 . A method for manufacturing a transistor, the method comprising the steps of:
 forming an oxide semiconductor layer over a substrate, the oxide semiconductor layer comprising indium, gallium, and zinc; and   crystallizing at least a part of the oxide semiconductor layer by heating.   
     
     
         7 . The method according to  claim 6 ,
 wherein the crystallization is performed by heating the oxide semiconductor layer at a temperature equal to or higher than 250° C. and equal to or lower than 700° C.   
     
     
         8 . The method according to  claim 6 , further comprising:
 adding oxygen to the oxide semiconductor layer.   
     
     
         9 . The method according to  claim 6 ,
 wherein the formation of the oxide semiconductor layer is performed while heating the substrate at a temperature equal to or higher than 150° C. and equal to or lower than 450° C.   
     
     
         10 . A method for manufacturing a transistor, the method comprising the steps of:
 forming an first insulating layer over a substrate;   forming an oxide semiconductor layer, a source electrode, and a drain electrode over the first insulating layer, the oxide semiconductor layer comprising indium, gallium, and zinc and including a crystalline region;   forming a second insulating layer over the oxide semiconductor layer, the source electrode, and the drain electrode;   forming a gate electrode over the second insulating layer; and   increasing the crystalline region by heating.   
     
     
         11 . The method according to  claims 10 ,
 wherein the increase in the crystalline region is performed by heating the oxide semiconductor layer at a temperature equal to or higher than 250° C. and equal to or lower than 700° C.   
     
     
         12 . The method according to  claim 10 , further comprising:
 adding oxygen to the oxide semiconductor layer.   
     
     
         13 . The method according to  claim 10 ,
 wherein the formation of the oxide semiconductor layer is performed while heating the substrate at a temperature equal to or higher than 150° C. and equal to or lower than 450° C.   
     
     
         14 . A method for manufacturing a transistor, the method comprising the steps of:
 forming an first insulating layer over a substrate;   forming an oxide semiconductor layer, a source electrode, and a drain electrode over the first insulating layer, the oxide semiconductor layer comprising indium, gallium, and zinc;   forming a second insulating layer over the oxide semiconductor layer, the source electrode, and the drain electrode;   forming a gate electrode over the second insulating layer; and   crystallizing at least a part of the oxide semiconductor layer by heating.   
     
     
         15 . The method according to  claim 14 ,
 wherein the crystallization is performed by heating the oxide semiconductor layer at a temperature equal to or higher than 250° C. and equal to or lower than 700° C.   
     
     
         16 . The method according to  claim 14 , further comprising:
 adding oxygen to the oxide semiconductor layer.   
     
     
         17 . The method according to  claim 14 ,
 wherein the formation of the oxide semiconductor layer is performed while heating the substrate at a temperature equal to or higher than 150° C. and equal to or lower than 450° C.   
     
     
         18 . A method for manufacturing a transistor, the method comprising the steps of:
 forming a gate electrode over a substrate;   forming a first insulating layer over the gate electrode;   forming an oxide semiconductor layer, a source electrode, and a drain electrode over the first insulating layer, the oxide semiconductor layer comprising indium, gallium, and zinc and including a crystalline region; and   increasing the crystalline region by heating.   
     
     
         19 . The method according to  claim 18 ,
 wherein the increase in the crystalline region is performed by heating the oxide semiconductor layer at a temperature equal to or higher than 250° C. and equal to or lower than 700° C.   
     
     
         20 . The method according to  claim 18 , further comprising:
 adding oxygen to the oxide semiconductor layer.   
     
     
         21 . The method according to  claim 18 ,
 wherein the formation of the oxide semiconductor layer is performed while heating the substrate at a temperature equal to or higher than 150° C. and equal to or lower than 450° C.   
     
     
         22 . A method for manufacturing a transistor, the method comprising the steps of:
 forming a gate electrode over a substrate;   forming a first insulating layer over the gate electrode;   forming an oxide semiconductor layer, a source electrode, and a drain electrode over the first insulating layer, the oxide semiconductor layer comprising indium, gallium, and zinc; and   crystallizing at least a part of the oxide semiconductor layer by heating.   
     
     
         23 . The method according to  claim 22 ,
 wherein the crystallization is performed by heating the oxide semiconductor layer at a temperature equal to or higher than 250° C. and equal to or lower than 700° C.   
     
     
         24 . The method according to  claim 22 , further comprising:
 adding oxygen to the oxide semiconductor layer.   
     
     
         25 . The method according to  claim 22 ,
 wherein the formation of the oxide semiconductor layer is performed while heating the substrate at a temperature equal to or higher than 150° C. and equal to or lower than 450° C.