Disclosed are a semiconductor device and a method of manufacturing the same. In the semiconductor device according to an exemplary embodiment of the present disclosure, at the time of forming a source electrode, a drain electrode, a field plate electrode, and a gate electrode on a substrate having a heterojunction structure such as AlGaN/GaN, the field plate electrode made of the same metal as the gate electrode is formed on the side surface of a second support part positioned below a head part of the gate electrode so as to prevent the gate electrode from collapsing and improve high-frequency and high-voltage characteristic of the semiconductor device.