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

A 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,
• wherein the gradient portion includes a first area adjoining the channel portion and a second area adjoining the conductorization portion, the first area including a first portion adjoining the channel portion and a second portion adjoining the second area, and
• wherein a first concentration gradient of the dopant in the first portion of the first area is greater than a second concentration gradient of the dopant in the second area, and the second concentration gradient is greater than a third concentration gradient of the dopant in the second portion of the first area.

A method for manufacturing a thin film transistor, the method comprising:

• forming an active layer;
• forming a gate insulating film on the active layer;
• forming a gate electrode partially overlapped with the active layer, the gate electrode formed on the gate insulating film through a patterning process using a photoresist pattern;
• and
• doping a dopant on the active layer,
• wherein the gate insulating film covers an upper surface of the active layer facing the gate electrode during doping of the active layer,
• the gate electrode is disposed in an area defined by the photoresist pattern in a plan view, and
• doping the dopant on the active layer further includes:
• first doping using the photoresist pattern as a mask, wherein the photoresist pattern is on the gate electrode and protrudes further than a side of the gate electrode;
• and
• second doping using the gate electrode as a mask after removing the photoresist pattern.