A High electron mobility transistor (HEMT) includes a source electrode, a gate electrode, a drain electrode, a channel forming layer in which a two-dimensional electron gas (2DEG) channel is induced, and a channel supplying layer for inducing the 2DEG channel in the channel forming layer. The source electrode and the drain electrode are located on the channel supplying layer. A channel increase layer is between the channel supplying layer and the source and drain electrodes. A thickness of the channel supplying layer is less than about 15 nm.