Method for fabricating a thin-film transistor

A method for fabricating a thin-film transistor, said method comprising the steps of:

• forming electrodes in at least a source region and a drain region on a substrate insulator;
• selectively dispersing a conductive material to form a small number of active species containing the conductive material only on the electrodes;
• selectively forming an impurity-contained semiconductor film on the electrodes by alternately repeating etching and deposition using a difference of deposition rate on the substrate insulator and on the electrodes which contain said active species;
• forming an active semiconductor layer covering the impurity-contained semiconductor film and the substrate insulator;
• forming a gate insulating film on the active semiconductor layer;
• forming a conductive layer for a gate on the gate insulating film;
• and
• patterning the conductive film, the gate insulating film, the active semiconductor layer, and the impurity-contained semiconductor film to define a gate region.

A method for fabricating a thin-film transistor, comprising the steps of:

• forming on a substrate a substrate insulator containing hydrogen or halogen entering from outside of the substrate insulator by increasing a content of the hydrogen or the halogen, respectively;
• laminating a first conductive film on the substrate insulator;
• patterning the first conductive film to form electrodes in at least a source region and a drain region;
• selectively forming an impurity-contained semiconductor film on a surface of each of the electrodes by alternately repeating etching with hydrogen plasma or halogen plasma, respectively, and deposition using a difference of deposition rate due to a deposition base;
• forming an active semiconductor layer on the substrate insulator and the impurity-contained semiconductor film;
• laminating an insulating film and a second conductive film in order on the active semiconductor layer;
• and
• patterning the the active semiconductor layer, the second conductive film, the insulating film, and the impurity-contained film to form a contact layer comprising the impurity-contained semiconductor film, a gate insulating film comprising the insulting film, and a gate electrode comprising the second conductive film.