Semiconductor device and liquid crystal display device

Abstract

A semiconductor device with a high reliability can be gained. The semiconductor device includes a substrate, a semiconductor layer, a gate insulating film and a gate electrode. The semiconductor layer is formed on the main surface of the substrate and includes source and drain regions adjoining each other via a channel region. The gate insulating film is formed on the channel region. The gate electrode is formed on the gate insulating film and has a sidewall. The gate insulating film includes an extended part which has sidewall positioned outside of the sidewall of the gate electrode. The source and the drain regions include high concentration impurity region which is formed in a region of the semiconductor layer apart from the sidewall of the extended part and low concentration impurity region, and which is formed in a region of the semiconductor layer positioned beneath the extended part.

What is claimed is:  
     
         1 . A semiconductor device including: 
 a substrate;    a semiconductor film which is formed on a main surface of said substrate and which includes source and drain regions adjoining each other via a channel region;    a gate insulating film formed on said channel region; and    a gate electrode which is formed on said gate insulating film and which has a sidewall, wherein 
 said gate insulating film includes an extended part which has a sidewall positioned outside of the sidewall of said gate electrode and  
 said source and drain regions include a high concentration impurity region which is formed in a region of said semiconductor film apart from the sidewall of said extended part and a low concentration impurity region of which the impurity concentration is relatively lower than that of said high concentration impurity region and which is formed in a region of said semiconductor film positioned beneath said extended part.  
   
     
     
         2 . The semiconductor device according to  claim 1 , wherein the sidewall of said extended part is formed so as to incline with respect to the main surface of said substrate.  
     
     
         3 . The semiconductor device according to  claim 1 , wherein 
 said gate insulating film includes an insulating film part which extends from the sidewall of said extended part to said high concentration impurity region and    the film thickness of said insulating film part is thinner than the film thickness of the extended part of said gate insulating film.    
     
     
         4 . The liquid crystal display device including a semiconductor device according to  claim 1 .  
     
     
         5 . A manufacturing method for a semiconductor device including: 
 the step of forming a semiconductor film on a substrate;    the step of forming an insulating film on said semiconductor film;    the step of forming a conductive film on said insulating film;    the step of forming a resist film which has a sidewall on said conductive film;    the step of forming a gate electrode which has a sidewall inside of the position of the sidewall of said resist film by partially removing said conductive film through etching using said resist film as a mask;    the step of forming a gate insulating film which includes an extended part having a sidewall positioned outside of the sidewall of said gate electrode by partially removing said insulating film through etching using said resist film as a mask;    the step of forming a high concentration impurity region of source and drain regions in a region of said semiconductor film apart from the sidewall of said extended part by injecting impurities into said semiconductor film using said resist film as a mask;    the step of removing said resist film; and    the step of forming, after the step of removing said resist film, a low concentration impurity region in source and drain regions, of which the impurity concentration is relatively lower than that of said high concentration impurity region, in regions of said semiconductor film positioned beneath said extended part by injecting impurities into said semiconductor film using said gate electrode as a mask.    
     
     
         6 . The manufacturing method for a semiconductor device according to  claim 5 , wherein in the step of forming said gate insulating film, insulating film part, of which the film thickness is thinner than the film thickness of the extended part of said gate insulating film, is made to remain on the semiconductor film which is to become said high concentration impurity region.  
     
     
         7 . The manufacturing method for a semiconductor device according to  claim 5 , wherein 
 the impurities which are injected into said low concentration impurity region and said high concentration impurity region are n type conductive impurities;    said gate electrode, said gate insulating film and said source and drain regions configure an n type thin film field effect transistor;    the manufacturing method further includes the step of forming a p type thin film field effect transistor which is carried out prior to the step of forming the gate electrode of said n type thin film field effect transistor; and    the step of forming said p type thin film field effect transistor includes; 
 the step of forming a resist film on said conductive film;  
 the step of forming a gate electrode of said p type thin film field effect transistor by partially removing said conductive film using said resist film as a mask and in addition, of making said conductive film remain on a region in which said n type thin film field effect transistor is to be formed; and  
 the step of forming source and drain regions of said p type thin film field effect transistor by injecting p type conductive impurities into said semiconductor film by using, as a mask, the gate electrode of said p type thin film field effect transistor and said conductive film which has been made to remain on the region in which said n type thin film field effect transistor is to be formed.  
   
     
     
         8 . The manufacturing method for a semiconductor device according to  claim 5 , wherein in the step of forming said gate insulating film, the sidewall of said extended part is formed so as to incline with respect to a main surface of said substrate.  
     
     
         9 . The manufacturing method for a semiconductor device according to  claim 8 , wherein in the step of forming said gate insulating film, the sidewall of said extended part are inclined with respect to the main surface of said substrate by partially removing said insulating film through isotropic etching.  
     
     
         10 . The manufacturing method for a semiconductor device according to  claim 8 , wherein in the step of forming said gate insulating film, the sidewall of said extended part is inclined with respect to the main surface of said substrate by using a resist receding method.  
     
     
         11 . The manufacturing method for a liquid crystal display device using a manufacturing method for a semiconductor device according to  claim 5 .  
     
     
         12 . A manufacturing method for a semiconductor device including: 
 the step of forming a semiconductor film on a substrate;    the step of forming an insulating film on said semiconductor film;    the step of forming a conductive film on said insulating film;    the step of forming a resist film which has a sidewall on said conductive film;    the step of forming a gate electrode which has a sidewall inside of the position of the sidewall of said resist film by partially removing said conductive film through etching using said resist film as a mask;    the step of forming a gate insulating film which includes extended parts having a sidewall positioned outside of the sidewall of said gate electrode by partially removing said insulating film through etching using said resist film as a mask;    the step of removing said resist film;    the step of forming a high concentration impurity region of source and drain regions in a region of said semiconductor film apart from the sidewall of said extended part by injecting impurities into said semiconductor film using said gate insulating film as a mask;    the step of forming a low concentration impurity region in source and drain regions, of which the impurity concentration is relatively lower than that of said high concentration impurity regions, in a region of said semiconductor film positioned beneath said extended part by injecting impurities into said semiconductor film using said gate electrode as a mask.    
     
     
         13 . The manufacturing method for a semiconductor device according to  claim 12 , wherein the step of forming said high concentration impurity region and the step of forming said low concentration impurity region are carried out simultaneously.  
     
     
         14 . The manufacturing method for a semiconductor device according to  claim 12 , wherein in the step of forming said gate insulating film, insulating film part, of which the film thickness is thinner than the film thickness of the extended part of said gate insulating film, is made to remain on the semiconductor film which is to become said high concentration impurity region.  
     
     
         15 . The manufacturing method for a semiconductor device according to  claim 12 , wherein 
 the impurities which are injected into said low concentration impurity region and said high concentration impurity region are n type conductive impurities;    said gate electrode, said gate insulating film and said source and drain regions configure an n type thin film field effect transistor;    the manufacturing method further includes the step of forming a p type thin film field effect transistor which is carried out prior to the step of forming the gate electrode of said n type thin film field effect transistor; and    the step of forming said p type thin film field effect transistor includes; 
 the step of forming a resist film on said conductive film;  
 the step of forming a gate electrode of said p type thin film field effect transistor by partially removing said conductive film using said resist film as a mask and in addition, of making said conductive film remain on a region in which said n type thin film field effect transistor is to be formed; and  
 the step of forming source and drain regions of said p type thin film field effect transistor by injecting p type conductive impurities into said semiconductor film by using, as a mask, the gate electrode of said p type thin film field effect transistor and said conductive film which has been made to remain on the region in which said n type thin film field effect transistor is to be formed.  
   
     
     
         16 . The manufacturing method for a semiconductor device according to  claim 12 , wherein in the step of forming said gate insulating film, the sidewall of said extended part is formed so as to incline with respect to a main surface of said substrate.  
     
     
         17 . The manufacturing method for a semiconductor device according to  claim 16 , wherein in the step of forming said gate insulating film, the sidewall of said extended part is inclined with respect to the main surface of said substrate by partially removing said insulating film through isotropic etching.  
     
     
         18 . The manufacturing method for a semiconductor device according to  claim 16 , wherein in the step of forming said gate insulating film, the sidewall of said extended part is inclined with respect to the main surface of said substrate by using a resist receding method.  
     
     
         19 . The manufacturing method for a liquid crystal display device using a manufacturing method for a semiconductor device according to  claim 12.