A thin film transistor substrate includes a substrate, a gate electrode on the substrate, an active layer on or below the gate electrode (the active layer at least partially overlapping the gate electrode) including a first active region and a second active region, the first active region and the second active region facing each other and extending beyond the gate electrode, a source electrode electrically connected to the first active region and a drain electrode electrically connected to the second active region, wherein the active layer includes a recess region which is at least partially recessed from a surface of the active layer facing the gate electrode, and the recess region includes a portion extending between the first active region and the second active region.