A diode device including a III-N compound layer is provided. The III-N compound layer has a channel region therein. A cathode region is located on the III-N compound layer. A first anode region is located on the III-N compound layer and extends into the III-N compound layer. The bottom of the first anode region is under the channel region. A second anode region is located on the III-N compound layer between the cathode region and the first anode region, and extends into the III-N compound material layer. The second anode region includes a high-energy barrier region. The high-energy barrier region adjoins a sidewall of the first anode region. A method for manufacturing a diode device is also provided.