Double-channel hemt device and manufacturing method thereof

An HEMT device (1), comprising: a semiconductor body (15) including a heterojunction structure (13); a dielectric layer (7) on the semiconductor body; a gate electrode (8); a drain electrode (12), facing a first side (8') of the gate electrode (8); and a source electrode (10), facing a second side (8") opposite to the first side (8') of the gate electrode; an auxiliary channel layer (20), which extends over the heterojunction structure (13) between the gate electrode (8) and the drain electrode (12), in electrical contact with the drain electrode (12) and at a distance from the gate electrode, and forming an additional conductive path for charge carriers that flow between the source electrode and the drain electrode.