Method for manufacturing a thin film transistor using steam anneal process to reinforce the surface of the ONO layer

A method for manufacturing a thin film transistor of a semiconductor device, comprising:

• forming a gate electrode after forming an insulation layer on a semiconductor substrate;
• performing a first pre-treatment cleaning process on the gate electrode and insulation layer, and then forming a lower oxidation layer;
• forming a nitride layer on the lower oxidation layer;
• forming an upper oxidation layer on the nitride layer to form a gate insulation layer comprised of the lower oxidation layer, the nitride layer and the upper oxidation layer;
• performing a steam thermal process using a wet-oxidation method on the gate insulation layer;
• removing the gate insulation layer around a node area of the semiconductor device by performing a masking and an etching processes;
• performing a second pre-treatment cleaning process on the gate insulation layer and insulation layer, and then forming a channel area on a remaining area excluding the node area;
• performing an SPG anneal process on the channel area, and performing a light oxidation for a surface treatment of the channel area by In-Situ;
• and
• performing a threshold voltage ion injection on the channel area, and then performing LDO ion injection and source/drain ion injection consecutively, using respective masks, on the channel area to form a pull-up transistor.