Method for manufacturing a polysilicon TFT with a variable thickness gate oxide

A method for manufacturing the polysilicon thin film transistor, comprising the steps of:

• forming a polysilicon layer on a transparent insulating substrate;
• forming a chemical vapor deposition oxide layer on the polysilicon layer;
• performing pre-thermal oxidation to form a thermal oxide layer under the chemical vapor deposition oxide layer;
• forming a gate electrode on the chemical vapor deposition oxide layer;
• performing post-thermal oxidation so that a first portion of the thermal oxide layer which exist under both sides of the gate electrode are thicker than a second portion of the thermal oxide layer;
• and
• forming a source and a drain regions by ion implantation.

A method for manufacturing the polysilicon thin film transistor, comprising the steps of:

• forming a polysilicon layer on a transparent insulating substrate;
• forming a first silicon oxide film on the polysilicon layer using a chemical vapor deposition method;
• forming a second silicon oxide film between the first silicon oxide film and the polysilicon layer by performing thermal oxidation;
• forming a gate electrode on a portion of the first silicon oxide film which lies on the second silicon oxide film;
• and
• performing thermal oxidation so that a first portion of the polysilicon layer under the gate electrode are thicker than a remaining second portion of the polysilicon layer.