A thin film transistor substrate, a display device, a method of manufacturing a thin film transistor substrate, and a method of manufacturing a display device, the thin film transistor substrate including a substrate; a first thin film transistor on the substrate, the first thin film transistor including a first active pattern, and a first gate electrode arranged to overlap at least a part of the first active pattern; and a second thin film transistor on the substrate, the second thin film transistor including a second active pattern that includes a plurality of protrusions on an upper surface thereof, and a second gate electrode arranged to overlap at least a part of the second active pattern.