Thin-film transistor and method of manufacturing thin-film transistor with tapered gate of 20 degrees or less

A method of manufacturing a thin-film transistor which comprises:

• a first step of forming a gate electrode on a main surface of a substrate;
• a second step of forming a gate insulating film on said substrate to cover said gate electrode;
• a third step of forming a semiconductor film formed on said gate insulating film to cross over said gate electrode;
• and
• a fourth step of laminating an interlayer insulting film formed on said semiconductor film, wherein,
• in said first step, said gate electrode is expanded in width toward said substrate such that said gate electrode forms a trapezoidal cross section, a base angle of said trapezoidal cross section is 20 degrees or less,
• in said second step, a silicon oxide film is laminated to a thickness of at least 1200 Å, and
• in said third step, an amorphous semiconductor film is polycrystallized by a laser annealing to form said semiconductor film.