Thin film transistor, method of fabricating the same, and organic light emitting diode display device including the thin film transistor

A method of fabricating a thin film transistor (TFT), comprising:

• forming a semiconductor layer on a substrate, the semiconductor layer including source and drain regions, each having a first metal catalyst crystallization region and a second metal catalyst crystallization region, and a channel region having the second metal catalyst crystallization region;
• forming a gate electrode in a position corresponding to the channel region of the semiconductor layer;
• forming a gate insulating layer between the semiconductor layer and the gate electrode to electrically insulate the semiconductor layer from the gate electrode;
• forming source and drain electrodes to be electrically connected to the source and drain regions, respectively;
• forming a first insulating layer under the source and the drain electrodes;
• and
• forming a second insulating layer over the source and drain electrodes.

An organic light emitting diode (OLED) display device comprising:

• a substrate;
• a semiconductor layer disposed on the substrate and including source and drain regions, each having a first metal catalyst crystallization region and a second metal catalyst crystallization region, wherein a grain size and structure of crystal grains of the first metal catalyst crystallization region differs from a grain size and structure of crystal grains of the second metal catalyst crystallization region, and a channel region having the second metal catalyst crystallization region;
• a gate electrode disposed in a position corresponding to the channel region of the semiconductor layer;
• a gate insulating layer interposed between the semiconductor layer and the gate electrode to electrically insulate the semiconductor layer from the gate electrode;
• source and drain electrodes electrically insulated from the gate electrode and electrically connected to the source and drain regions, respectively;
• and
• a first electrode, an organic layer, and a second electrode electrically connected to the source and drain electrodes.

A method of forming a semiconductor layer including a first metal catalyst crystallization region and a second metal catalyst crystallization region, the method comprising:

• forming a first amorphous silicon layer on a substrate;
• forming a metal catalyst layer on the first amorphous silicon layer;
• annealing the substrate having the first amorphous silicon layer formed thereon such that the first amorphous silicon layer is crystallized to form the first metal catalyst crystallization region;
• forming a second amorphous silicon layer on the first metal catalyst crystallization region;
• and
• annealing the substrate having the first metal catalyst crystallization region and the second amorphous silicon layer formed thereon such that the second amorphous silicon layer is crystallized to form the second metal catalyst crystallization region.