Thin-film transistor and method for fabricating same and liquid crystal display device

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

• forming a gate electrode on a substrate;
• forming a gate insulation film on the gate electrode;
• forming a layer, on the gate insulation film, which is used to form an operative semiconductor film;
• forming an insulation film having a first predetermined pattern on the layer;
• doping the layer not covered by the insulation film having the first pattern with impurity to form semiconductor films doped with impurity, the portion of the layer covered by the insulation film having the first pattern not doped with impurity forms the operative semiconductor film;
• removing the insulation film having the first pattern and forming another insulation film having a second pattern larger than the first pattern forming a channel protection film covering the operative semiconductor film and at least part of the doped semiconductor films, the part of the doped semiconductor films covered by the channel protection film form semiconductor contact portions;
• and
• forming a source electrode and a drain electrode connected to the semiconductor contact portions.