Disclosed are a thin film transistor including a gate electrode, a semiconductor layer, a source electrode, and a drain electrode. The semiconductor layer overlaps the gate electrode. The source electrode and the drain electrode are electrically connected to the semiconductor layer. The semiconductor layer includes a first semiconductor layer including a first organic semiconductor material and a second semiconductor layer including a second organic semiconductor material. The second semiconductor layer is farther spaced apart from the gate electrode than the first semiconductor layer. A HOMO energy level of the second organic semiconductor material is different from a HOMO energy level of the first organic semiconductor material. A method of manufacturing the thin film transistor is disclosed.