A thin film transistor includes a substrate, a gate electrode disposed on the substrate, an active pattern disposed on the gate electrode, a source electrode electrically coupled to the active pattern and a drain electrode electrically coupled to the active pattern. The active pattern includes a first channel layer overlapping the source electrode and the drain electrode and a second channel layer overlapping the gate electrode. The second channel layer includes a plurality of high electron mobility regions. An electron mobility of each of the high electron mobility regions is greater than an electron mobility of the first channel layer.