Manufacturing method of semiconductor device

Abstract

To provide a highly reliable semiconductor device manufactured by giving stable electric characteristics to a semiconductor device including an oxide semiconductor. In a manufacturing process of a transistor, an oxide semiconductor layer, a source electrode layer, a drain electrode layer, a gate insulating film, a gate electrode layer, and an aluminum oxide film are formed in this order, and then heat treatment is performed on the oxide semiconductor layer and the aluminum oxide film, whereby an oxide semiconductor layer from which an impurity containing a hydrogen atom is removed and which includes a region containing oxygen more than the stoichiometric proportion is formed. In addition, when the aluminum oxide film is formed, entry and diffusion of water or hydrogen into the oxide semiconductor layer from the air due to heat treatment in a manufacturing process of a semiconductor device or an electronic appliance including the transistor can be prevented.

1 . (canceled) 
     
     
         2 . A method for manufacturing a semiconductor device comprising the steps of:
 forming an oxide semiconductor layer;   forming a source electrode layer and a drain electrode layer over the oxide semiconductor layer;   forming a gate insulating film adjacent to the oxide semiconductor layer after forming the source electrode layer and the drain electrode layer;   forming a gate electrode layer adjacent to the oxide semiconductor layer with the gate insulating film interposed therebetween;   adding an impurity element to the oxide semiconductor layer using the source electrode layer, the drain electrode layer, and the gate electrode layer as masks after forming the gate insulating film and the gate electrode layer; and   forming an aluminum oxide film over the gate electrode layer.   
     
     
         3 . The method for manufacturing a semiconductor device, according to  claim 2 , further comprising the step of performing heat treatment on the oxide semiconductor layer after the oxide semiconductor layer is formed. 
     
     
         4 . The method for manufacturing a semiconductor device, according to  claim 2 , further comprising the step of forming an interlayer insulating film over the aluminum oxide film. 
     
     
         5 . The method for manufacturing a semiconductor device, according to  claim 4 , wherein the interlayer insulating film is formed of silicon oxynitride. 
     
     
         6 . The method for manufacturing a semiconductor device, according to  claim 2 , wherein the oxide semiconductor layer is formed while being heated. 
     
     
         7 . The method for manufacturing a semiconductor device, according to  claim 2 , wherein the gate insulating film includes a region in which an oxygen content is higher than a stoichiometric proportion of the gate insulating film. 
     
     
         8 . The method for manufacturing a semiconductor device, according to  claim 2 , wherein a channel length determined by a distance between the source electrode layer and the drain electrode layer which are adjacent to each other over the oxide semiconductor layer is less than or equal to 2 μm. 
     
     
         9 . The method for manufacturing a semiconductor device, according to  claim 2 , wherein an inert gas is changed to a gas containing oxygen during the heat treatment. 
     
     
         10 . A method for manufacturing a semiconductor device comprising the steps of:
 forming a base insulating film;   forming an oxide semiconductor layer over the base insulating film;   forming a source electrode layer and a drain electrode layer over the oxide semiconductor layer;   forming a gate insulating film adjacent to the oxide semiconductor layer after forming the source electrode layer and the drain electrode layer;   forming a gate electrode layer adjacent to the oxide semiconductor layer with the gate insulating film interposed therebetween;   adding an impurity element to the oxide semiconductor layer using the source electrode layer, the drain electrode layer, and the gate electrode layer as masks after forming the gate insulating film and the gate electrode layer; and   forming a metal oxide film over the gate electrode layer.   
     
     
         11 . The method for manufacturing a semiconductor device, according to  claim 10 , further comprising the step of performing heat treatment on the oxide semiconductor layer after the oxide semiconductor layer is formed. 
     
     
         12 . The method for manufacturing a semiconductor device, according to  claim 10 , further comprising the step of forming an interlayer insulating film over the metal oxide film. 
     
     
         13 . The method for manufacturing a semiconductor device, according to  claim 12 , wherein the interlayer insulating film is formed of silicon oxynitride. 
     
     
         14 . The method for manufacturing a semiconductor device, according to  claim 10 , wherein the oxide semiconductor layer is formed while being heated. 
     
     
         15 . The method for manufacturing a semiconductor device, according to  claim 10 , wherein the gate insulating film includes a region in which an oxygen content is higher than a stoichiometric proportion of the gate insulating film. 
     
     
         16 . The method for manufacturing a semiconductor device, according to  claim 10 , wherein a channel length determined by a distance between the source electrode layer and the drain electrode layer which are adjacent to each other over the oxide semiconductor layer is less than or equal to 2 μm. 
     
     
         17 . The method for manufacturing a semiconductor device, according to  claim 10 , wherein an inert gas is changed to a gas containing oxygen during the heat treatment.