Patent ID: 8501554

Claim:
A method for manufacturing a thin film transistor, comprising the steps of: forming a gate insulating layer over a gate electrode layer; forming a semiconductor layer over the gate insulating layer; forming an impurity semiconductor layer over the semiconductor layer; forming a patterned semiconductor layer comprising the semiconductor layer and the impurity semiconductor layer by using a first resist mask, the patterned semiconductor layer overlapping at least a part of the gate electrode layer; forming a conductive layer over the gate insulating layer and the patterned semiconductor layer; etching the conductive layer to form source and drain electrode layers by using a second resist mask over the conductive layer; etching the impurity semiconductor layer of the patterned semiconductor layer, to expose a part of the semiconductor layer so that a back channel portion in the thin film transistor is formed; removing the second resist mask after etching the impurity semiconductor layer of the patterned semiconductor layer; and performing a plasma treatment on a surface of the back channel portion to remove contamination materials from the surface of the back channel portion, after removing the second resist mask.