To provide a high-electron mobility transistor and manufacturing method thereof whereby the parasitic capacitance of the gate is reduced to improve the high frequency characteristics.

This high-electron mobility transistor comprises an upper and lower wide band gap layers on the upper and lower faces of a channel layer for forming an electron gas layer having a substantially uniform density, Si planner doping layers, 25a, 23a formed respectively in the upper and lower wide band gap layers 25, a drain-source electrode contact layer formed on the upper on the upper band gap layer, T-shaped gate electrodes 29 formed in recesses formed so as to separate the electrode contact layer 26, and passivation film 28 covering the insides of the recesses and lower parts of the gate electrodes.