Thin-film transistor

Abstract

A gate-insulated thin film transistor is disclosed. One improvement is that the thin film transistor is formed on a substrate through a blocking layer in between so that it is possible to prevent the transistor from being contaminated with impurities such as alkali ions which exist in the substrate. Also, a halogen is added to either or both of the blocking lay r and a gate insulator of the transistor.

1 . A semiconductor device comprising:
 a glass substrate;   a protective film formed over the glass substrate;   a non-single-crystalline semiconductor film formed over the protective film and including source and drain regions and a channel region formed between the source and drain regions, and   a gate electrode adjacent to the channel region with a gate insulator therebetween,   wherein the protective film includes a halogen element.   
   
   
       2 . The semiconductor device of  claim 1 , wherein the non-single-crystalline semiconductor film comprises crystalline silicon. 
   
   
       3 . The semiconductor device of  claim 1 , wherein the protective film comprises silicon oxide. 
   
   
       4 . The semiconductor device of  claim 1 , wherein the gate electrode is located over the channel region. 
   
   
       5 . The semiconductor device of  claim 1 , wherein the protective film is 500 Å-5000 Å thick. 
   
   
       6 . A semiconductor device comprising:
 a glass substrate;   a protective film formed over the glass substrate;   a semiconductor film formed over the protective film and including source, drain and channel regions;   a gate electrode formed over the channel region with a gate insulator therebetween; and   wherein the protective film contains a halogen element at a concentration not higher than 5 atom %.   
   
   
       7 . The semiconductor device of  claim 6 , wherein the gate insulator and the protective film comprises a same insulating material with each other. 
   
   
       8 . A semiconductor device comprising:
 a glass substrate;   a protective film formed over the glass substrate;   a non-single-crystalline semiconductor film formed over the protective film and including source, drain and channel regions;   a gate electrode adjacent to the channel region with a gate insulator therebetween,   wherein each of the gate insulator and the protective film contains a halogen element.   
   
   
       9 . The semiconductor device of  claim 8 , wherein the halogen element is selected from the group consisting of fluorine or chlorine. 
   
   
       10 . The semiconductor device of  claim 8 , wherein the channel region comprises polycrystalline silicon. 
   
   
       11 . The semiconductor device of  claim 8 , wherein the channel region comprises microcrystalline silicon. 
   
   
       12 . The semiconductor device of  claim 8 , wherein the halogen element is contained at a concentration not higher than 5 atom %. 
   
   
       13 . A semiconductor device comprising:
 a glass substrate;   a protective film comprising silicon oxide formed on and in contact with the glass substrate;   a semiconductor film formed over the protective film and including source and drain regions and a channel region extending therebetween;   a gate insulator formed over the channel region; and   a gate electrode formed over the gate insulator,   wherein the protective film contains a halogen element and directly contacts the semiconductor film.   
   
   
       14 . The semiconductor device of  claim 13 , wherein the halogen element is contained in the protective film at a concentration of not lower than 0.1 atom %.