Patent ID: 8318554

Claim:
A manufacturing method of a thin film transistor, comprising the steps of: forming a base insulating film over a glass substrate; forming a pattern of a semiconductor film containing silicon over the base insulating film, wherein the pattern of the semiconductor film has a tapered shape at an edge portion of the pattern; forming a first insulating film by performing plasma oxidation using high electron density plasma with a frequency of 2.45 GHz to the pattern of the semiconductor film with a condition where a temperature of the glass substrate is set at a temperature 100° C. or more lower than a strain point of the glass substrate so that a thickness of a top portion of the first insulating film, a thickness of a side portion of the first insulating film and a corner portion of the first insulating film are same; forming a second insulating film containing nitrogen over the first insulating film by a CVD method; performing plasma nitridation to the second insulating film; forming a gate electrode over the second insulating film, wherein oxygen gas, hydrogen gas and an inert gas are provided to perform plasma oxidation, and wherein the base insulating film is formed with plasma nitridation of the glass substrate so as to form a silicon nitride or silicon nitride containing oxygen.