Thin film transistor and method of manufacturing the same

A method of manufacturing a thin film transistor comprising:

• a substrate,
• a gate electrode formed on said substrate;
• an insulating film formed on said gate electrode and said substrate except for whole of outer surface of said gate electrode,
• a semiconductor film formed on said insulating film,
• a source electrode connected to said semiconductor film, and
• a drain electrode connected to said semiconductor film,
• wherein at least one of said gate electrode, said source electrode, and said drain electrode, is composed of one material, and the method of manufacturing comprises the steps of:
• (a) changing an etching rate of said at least one electrode in a direction perpendicular to a top surface thereof by changing deposition conditions during a deposition step, and
• (b) etching said at least one electrode such that it is trapezoidal in its section;
• wherein said changing step includes either (i) changing a deposition pressure, (ii) changing a deposition power, (iii) changing a deposition temperature, (iv) changing a partial pressure of nitrogen gas relative to argon gas of a deposition gas stream, or (v) doping a deposition gas stream with phosphorous ions.