Active matrix substrate and manufacturing method of the same

Abstract

To reduce the number of photolithography processes in manufacturing an active matrix substrate. Provided is a TFT substrate which has a pixel electrode connected to a drain electrode of a TFT, a source line connected to a source electrode of the TFT, and a gate line connected to a gate electrode of the TFT. A source electrode, a drain electrode, and a source line include a conductive film of the same layer as the pixel electrode. Under the source line and the pixel electrode, there remains a semiconductor layer of the same layer as a semiconductor film which constitutes a channel part of the TFT substrate.

What is claimed is: 
     
         1 . An active matrix substrate comprising a thin film transistor,
 said thin film transistor including:
 a semiconductor film formed on a substrate; 
 a source electrode and a drain electrode formed on said semiconductor film; 
 a channel part which is a part of said semiconductor film and is exposed between said source electrode and said drain electrode; 
 an insulation film covering said source electrode, said drain electrode, and said channel part; and 
 a gate electrode disposed above said channel part with an insulation film interposed therebetween, 
   said active matrix substrate further comprising:   a pixel electrode connected to said drain electrode of said thin film transistor;   a source line connected to said source electrode of said thin film transistor; and   a gate line connected to said gate electrode of said thin film transistor,   wherein said source electrode, said drain electrode, and said source line include a conductive film of the same layer as said pixel electrode, and   wherein a semiconductor layer of the same layer as said semiconductor film remains under said source line and said pixel electrode.   
     
     
         2 . The active matrix substrate of  claim 1 , further comprising:
 a source terminal provided on an end part of said source line;   a gate terminal provided on an end part of said gate line, said insulation film further covering said source line and said source terminal; and   a source terminal pad formed on said insulation film and of a conductive film of the same layer as said gate terminal, said source terminal pad connected to said source terminal through a contact hole.   
     
     
         3 . The active matrix substrate of  claim 1 , wherein said semiconductor film is made of a transparent oxide semiconductor, and said pixel electrode is made of a transparent conductive film. 
     
     
         4 . The active matrix substrate of  claim 1 , wherein said source electrode, said drain electrode, and said source line further include a metal film on said conductive film of the same layer as said pixel electrode. 
     
     
         5 . The active matrix substrate of  claim 1 , further comprising:
 a common electrode made of a transparent conductive film provided above said pixel electrode with said insulation film interposed therebetween.   
     
     
         6 . The active matrix substrate of  claim 5 , wherein said common electrode has a comb shape having slits or a lattice shape. 
     
     
         7 . The active matrix substrate of  claim 5 , wherein said gate electrode and said gate line include a conductive film of the same layer as said common electrode. 
     
     
         8 . The active matrix substrate of  claim 7 , wherein said gate electrode and said gate line further include a metal film on said conductive film of the same layer as said common electrode. 
     
     
         9 . The active matrix substrate of  claim 5 , further comprising:
 a common line formed of a conductive film of the same layer as said common electrode and configured to supply a common potential to said common electrode.   
     
     
         10 . The active matrix substrate of  claim 9 , further comprising:
 a redundant common line formed of a conductive film of the same layer as said source line and parallel-connected to said common line.   
     
     
         11 . The active matrix substrate of  claim 9 , wherein said common line further includes a metal film on said conductive film of the same layer as said common electrode. 
     
     
         12 . A manufacturing method of an active matrix substrate equipped with:
 a thin film transistor;   a pixel electrode connected to a drain electrode of said thin film transistor;   a source line connected to a source electrode of said thin film transistor; and   a source terminal provided on an end part of said source line, the manufacturing method comprising the steps of:   (a) forming on a substrate a first laminated film in which a semiconductor film, a first transparent conductive film, and a first metal film are laminated in this order;   (b) forming on said first laminated film a first photoresist pattern having a first part covering a formation area of a channel part of said thin film transistor, a second part which is thicker than said first part and covers a formation area of said pixel electrode, and a third part which is thicker than said second part and covers formation areas of said source electrode, said drain electrode, said source line, and said source terminal;   (c) patterning said first metal film, said first transparent conductive film, and said semiconductor film by using said first photoresist pattern as a mask;   (d) reducing, after said step (c), a thickness of said first photoresist pattern to remove said first part, and then patterning said first metal film and said first transparent conductive film by using remaining of the first photoresist pattern as a mask; and   (e) further reducing, after said step (d), a thickness of said first photoresist pattern to remove said second part, and then patterning said first metal film by using remaining of said first photoresist pattern as a mask.   
     
     
         13 . The manufacturing method of an active matrix substrate of  claim 12 , wherein said active matrix substrate is further equipped with:
 a gate line connected to a gate electrode of said thin film transistor;   a gate terminal provided on an end part of said gate line;   a common electrode disposed to face said pixel electrode; and   a source terminal pad provided on said source terminal,   the manufacturing method comprising the steps of:   (f) forming, after removing said first photoresist pattern, an insulation film on said substrate and then forming a contact hole in a formation area of said source terminal on said insulation film;   (g) forming on said insulation film including an inside of said contact hole, a second laminated film in which a second transparent conductive film and a second metal film are laminated in this order;   (h) forming on said second laminated film a second photoresist pattern which has a first part covering formation areas of said common electrode, said gate terminal, and said source terminal pad and which has a second part being thicker than said first part and covering a formation area of said gate electrode and said gate line;   (i) patterning said second metal film and said second transparent conductive film by using said second photoresist pattern as a mask; and   (j) reducing, after said step (i), a thickness of said second photoresist pattern to remove said first part, and patterning said second metal film by using remaining of said second photoresist pattern as a mask.