According to example embodiments, a high electron mobility transistor (HEMT) includes a channel layer; a channel supply layer on the channel layer; a source electrode and a drain electrode spaced apart from each other on one of the channel layer and the channel supply layer; a gate electrode on a part of the channel supply layer between the source electrode and the drain electrode; a first depletion-forming layer between the gate electrode and the channel supply layer; and a at least one second depletion-forming layer on the channel supply layer between the gate electrode and the drain electrode. The at least one second depletion-forming layer is electrically connected to the source electrode.