The present application discloses a thin film transistor including a base substrate; an active layer on the base substrate having a channel region, a source electrode contact region, and a drain electrode contact region; an etch stop layer on a side of the channel region distal to the base substrate covering the channel region; a source electrode on a side of the source electrode contact region distal to the base substrate; and a drain electrode on a side of the drain electrode contact region distal to the base substrate. A thickness of the active layer in the source electrode contact region and the drain electrode contact region is substantially the same as a combined thickness of the active layer in the channel region and the etch stop layer.