Liquid crystal display and method of manufacturing the same

Abstract

A method of manufacturing a liquid crystal display device is intended to decrease the number of manufacturing steps. The liquid crystal display device is arranged so that in each pixel area provided on a liquid-crystal-side surface of one of a pair of substrates disposed to oppose each other with a liquid crystal interposed therebetween, a signal from a drain line is applied to a pixel electrode via a drain electrode and a source electrode which are formed in a layer overlying a semiconductor layer of a thin film transistor, by the supply of a scanning signal from a gate electrode which is positioned as an underlying layer with respect to the semiconductor layer. The method of manufacturing such liquid crystal display device includes the steps of: forming a stacked structure in which the semiconductor layer and a first conductive layer are sequentially stacked in the same pattern, in both an area for forming the drain signal and an area for forming the thin film transistor; and after forming a second conductive layer, by using the same mask, providing separation between the drain electrode and the source electrode of the thin film transistor and also forming the pixel electrode connected to the source electrode.

What is claimed is:  
     
         1 . A method of manufacturing a liquid crystal display device comprising a pair of substrates having a liquid crystal layer disposed therebetween, a plurality of pixel areas provided on a liquid-crystal-side surface of one of said pair of substrates, each pixel area including a pixel electrode, a drain and a source electrode formed in a layer overlying a semiconductor layer of a thin film transistor, and a gate electrode disposed in a layer underlying said semiconductor layer, each said pixel area having an associated drain line for receiving a signal and applying said signal to said pixel electrode via said drain and source electrodes in response to a scanning signal applied to said gate electrode, said method comprising: 
 forming a stacked structure comprising a first conductive layer disposed over said semiconductor layer, said first conductive layer and said semiconductor layer having the same pattern;    forming a second conductive layer over said stacked structure; and    removing a portion of said second conductive layer to form said pixel electrode and removing a portion of said stacked structure to form a first portion separate from a second portion, said first portion being said drain electrode, said second portion being said source electrode, said pixel electrode being in electrical communication with said source electrode.    
     
     
         2 . The method of manufacturing a liquid crystal display device according to    claim 1    further including retaining a portion of said second conductive layer that is disposed over said drain electrode as a disconnection-preventing signal line.  
     
     
         3 . The method of manufacturing the liquid crystal display device according to    claim 1    further including forming a contact layer under said drain electrode and said source electrode.  
     
     
         4 . The method of manufacturing the liquid crystal display device according to    claim 3    wherein said contact layer is a p-doped semiconductor layer.  
     
     
         5 . A method of forming a liquid crystal display device, comprising the steps of: 
 forming a gate line and a counter electrode on a face of a substrate;    forming an insulating film over said gate line and said counter electrode;    forming a semiconductor layer and a metal layer over said insulating film;    etching said semiconductor layer and said metal layer to produce the same pattern;    forming a transparent conductive film over said semiconductor layer and said metal layer;    etching said transparent conductive film to form a pixel electrode and to expose a portion of said metal layer; and    etching said exposed portion of said metal layer to form a drain electrode and a source electrode;    wherein said drain electrode is separated from said source electrode and said source electrode is connected to said pixel electrode.    
     
     
         6 . The method of manufacturing the liquid crystal display device according to    claim 5    wherein said pixel electrode is a comb-shaped structure, and said counter electrode is a stripe-shaped structure.  
     
     
         7 . The method of manufacturing the liquid crystal display device according to    claim 5    wherein said transparent conductive film is ITO.  
     
     
         8 . The method of manufacturing the liquid crystal display device according to    claim 5    wherein said transparent conductive film is IZO.  
     
     
         9 . A method of forming a display device, comprising the steps of: 
 forming a gate line and a counter voltage signal line on a face of a substrate;    forming an insulating film over said gate line and said counter voltage signal line;    forming a multi-layered structure comprising a semiconductor layer disposed over said insulating film and a metal layer disposed over said semiconductor layer;    forming a transparent conductive film over said multi-layered structure;    removing some of said transparent conductive film to form a pixel electrode;    removing some of said metal layer to form a drain electrode and a source electrode;    forming a protective film to cover at least an area in which said pixel electrode is formed;    forming a counter electrode connected to said counter voltage signal line on an upper surface of said protective film;    wherein said drain electrode is separate from said source electrode and said source electrode is connected to said pixel electrode.    
     
     
         10 . The method of manufacturing the liquid crystal display device according to    claim 9    wherein said pixel electrode is a comb-shaped structure, and said counter electrode is a stripe-shaped structure.  
     
     
         11 . The method of manufacturing a liquid crystal display device according to    claim 9    wherein said removing said transparent conductive film includes retaining a portion thereof as a disconnection-preventing signal line formed on said drain electrode, 
 wherein said disconnection-preventing signal line is the same material as that of said pixel electrode.  
 
     
     
         12 . The method of manufacturing a liquid crystal display device according to    claim 9    wherein said semiconductor layer is an amorphous silicon layer.  
     
     
         13 . The method of manufacturing a liquid crystal display device according to    claim 9    wherein said transparent conductive film is ITO.  
     
     
         14 . The method of manufacturing a liquid crystal display device according to    claim 9    wherein said transparent conductive film is IZO.  
     
     
         15 . A method of manufacturing a liquid crystal display device which includes at least one pixel area provided on a liquid-crystal-side surface of one of a pair of substrates, a liquid crystal interposed between said pair of substrates, a thin film transistor to be driven by a scanning signal from a gate line, a pixel electrode for receiving a video signal from a drain line supplied via said thin film transistor; a counter electrode connected to a counter voltage signal line for generating an electric field having a component parallel to said substrates between said counter electrode and said pixel electrode, said thin film transistor being a stacked structure comprising a sequential stacking of a gate electrode, an insulating film, a semiconductor layer, a drain electrode and a source electrode, said gate electrode being connected to said gate line, said drain electrode being connected to said drain line, said source electrode being connected to said pixel electrode, said manufacturing method comprising the steps of: 
 forming said gate line and said counter voltage signal line on a first surface of said substrate;    depositing said insulating film, said semiconductor layer, and drain line;    etching said semiconductor layer and said drain line a first pattern;    forming said source electrode and said drain electrode connected to said drain line;    forming said pixel electrode connected to said source electrode, said pixel electrode comprising a transparent conductive film; and    forming a counter electrode which is disposed over said pixel electrode with a protective film interposed therebetween and is connected to said counter voltage signal line.    
     
     
         16 . The method of manufacturing the liquid crystal display device according to    claim 15    wherein said step of forming said pixel electrode includes forming a disconnection-preventing signal line superposed on said drain line.  
     
     
         17 . The method of manufacturing the liquid crystal display device according to    claim 15    wherein said semiconductor layer is an amorphous silicon layer.  
     
     
         18 . The method of manufacturing the liquid crystal display device according to    claim 15    wherein said transparent conductive film is ITO.  
     
     
         19 . The method of manufacturing the liquid crystal display device according to    claim 15    wherein said transparent conductive film is IZO.  
     
     
         20 . The method of manufacturing the liquid crystal display device according to    claim 15    further including of forming a contact layer on a surface of said semiconductor layer to provide separation between said drain electrode and said source electrode of said thin film transistor, 
 forming said pixel electrode connected to said source electrode, and  
 etching a portion of said contact layer that is exposed from said drain electrode and said source electrode.