Thin film semiconductor divice, display device using such thin film semiconductor device and manufacturing method thereof

Abstract

A thin film semiconductor device formed as integrated circuits on an insulating substrate with bottom gate type thin film transistors stacked with gate electrodes, a gate insulating film and a semiconductor thin film in the order from below upward. The gate electrodes comprise metallic materials with thickness less than 100 nm. The gate insulating film has a thickness thicker than the gate electrodes. The semiconductor thin film comprises polycrystalline silicon crystallized by a laser beam. By reducing thickness of metallic gate electrodes, thermal capacity becomes small and difference in thermal condition on the metallic gate electrodes and on the insulating substrate made of glass or the like becomes small. This invention relates to the task of uiforming and optimizing recrystallization by a laser anneal treatment provided for the semiconductor thin film which works as an active layer of the bottom gate type thin film transistors.

What is claimed is:  
     
         1 . A thin film semiconductor device comprising: 
 an insulating substrate; and    a thin film transistor formed on said insulating substrate, wherein    said thin film transistor is formed in a bottom gate structure having gate electrode, a gate insulating film, and a semiconductor thin film stacked in the order from below upward, and    said gate electrode is made of metallic material having a thickness of less than 100 nm.    
     
     
         2 . The thin film semiconductor device according to    claim 1   , wherein 
 said gate insulating film has a thickness thicker than the thickness of said gate electrode.    
     
     
         3 . The thin film semiconductor device according to    claim 1   , wherein 
 said semiconductor thin film comprises polycrystalline silicon crystallized by an irradiation of a laser beam.    
     
     
         4 . The thin film semiconductor device according to    claim 1   , wherein 
 said gate electrode has a multi-layered structure stacked with an upper layer having comparatively low heat conductivity and high electric resistance, and a lower layer having comparatively high heat conductivity and low electric resistance.    
     
     
         5 . A display device comprising: 
 an insulating substrate;    pixels arranged in a matrix form; and    thin film transistors for driving said respective pixels, wherein    said pixels and said thin film transistors are formed as integrated circuits on said insulating substrate,    each of said thin film transistors has a bottom gate structure having a gate electrode, a gate insulating film and a semiconductor thin film stacked in the order from below upward, and    said gate electrode is made of metallic material having a thickness of less than 100 nm.    
     
     
         6 . The display device according to    claim 5   , wherein 
 said gate insulating film has a film thickness thicker than the thickness of the gate electrode.    
     
     
         7 . The display device according to    claim 5   , wherein 
 said semiconductor thin film comprises polycrystalline silicon crystallized by an irradiation of a laser beam.    
     
     
         8 . The display device according to    claim 5   , wherein 
 said gate electrodes have a multi-layer structure stacked with an upper layer having comparatively low heat conductivity and high electric resistance, and a lower layer having comparatively high heat conductivity and low electric resistance.    
     
     
         9 . The method of manufacturing a display device having pixels arranged in a matrix form and thin film transistors for driving said respective pixels formed as integrated circuits on an insulating substrate, said method comprising the step of: 
 stacking a gate electrode, a gate insulating film and a semiconductor thin film in the order from below upward on an insulating substrate to form a thin film transistor in bottom gate structure, wherein    said gate electrode formed of metallic material has a thickness of less than 100 nm.    
     
     
         10 . The method according to    claim 9   , wherein 
 said gate insulating film is formed with a thickness thicker than the thickness of the gate electrode.    
     
     
         11 . The method according to    claim 9    wherein 
 said semiconductor thin film uses polycrystalline silicon crystallized by an irradiation of a laser beam.  
 
     
     
         12 . The method according to    claim 9   , wherein 
 said gate electrode is formed by stacking an upper layer having comparatively low heat conductivity and high electric resistance and a lower layer having comparatively high heat conductivity and low electric resistance.