A thin film transistor substrate including a plurality of thin film transistors, and a flat panel display apparatus. Each of the plurality of thin film transistors includes an active layer comprising a first channel region having a first plurality of protrusion lines arranged therein and a second channel region and having a second plurality of protrusion lines arranged therein, a source electrode and a drain electrode electrically connected to the active layer and a gate electrode insulated from the active layer, wherein the first and second plurality of protrusion lines extend in a first direction, wherein a edges of the first channel region that extend in the first direction and are offset sideways by a distance in a second direction that is orthogonal to the first direction from corresponding edges of the second channel region that extend in the first direction.