Thin film transistor, method for manufacturing the thin film transistor and display device comprising the thin film transistor

A thin film transistor and a method for manufacturing the same are disclosed, wherein the thin film transistor comprising an active layer, a gate electrode spaced apart from the active layer and partially overlapped with the active layer, and a gate insulating film between the active layer and the gate electrode, wherein the active layer includes a channel portion overlapped with the gate electrode, a conductorization portion which is not overlapped with the gate electrode, and a gradient portion between the channel portion and the conductorization portion and not overlapped with the gate electrode, the conductorization portion and the gradient portion of the active layer are doped with a dopant, the gate insulating film covers an upper surface of the active layer facing the gate electrode during doping of the active layer, and in the gradient portion, a concentration of the dopant increases along a direction from the channel portion toward the conductorization portion. A display device comprising the thin fi