A thin film transistor includes a substrate; a semiconductor layer disposed on the substrate, the semiconductor layer having a source region, a drain region, and a channel region between the source region and the drain region; a gate insulating layer disposed on the semiconductor layer and on the substrate; and a gate electrode disposed on the insulating layer over the channel region, wherein the semiconductor layer includes tapered edge portions with a taper angle defined between the tapered edge portions and a surface of the substrate is less than about 30 degrees.