A display device may include a first gate electrode disposed on a substrate, a buffer layer disposed on the first gate electrode, a first active pattern on the buffer layer, the first active pattern overlapping the first gate electrode and including an oxide semiconductor, a second active pattern on the buffer layer, spaced apart from the first active pattern, and including an oxide semiconductor, the second active pattern including a channel region, and a source region and a drain region, a source pattern and a drain pattern respectively at ends of the first active pattern, a first insulation pattern disposed on the first active pattern, a second insulation pattern disposed on the channel region, a first oxygen supply pattern on the first insulation pattern, a second oxygen supply pattern on the second insulation pattern, and a second gate electrode on the second oxygen supply pattern.