A method for manufacturing an ohmic contact for a HEMT device, comprising the steps of: - forming a sacrificial structure (28; 60) on a semiconductor body comprising a heterostructure; - forming, through the sacrificial structure (28; 60), an opening (35; 42), through which a surface region of the semiconductor body is exposed at said heterostructure; - etching the surface region of the semiconductor body using said sacrificial structure (28; 60) as etching mask to form a trench in the heterostructure; - depositing one or more metal layers (22a, 22b; 22) in said trench and on the sacrificial structure (28; 60); and - carrying out a lift-off process of the sacrificial structure (28; 60), wherein the semiconductor body comprises a substrate, a channel layer on the substrate, a barrier layer on the channel layer, and a protection layer on the barrier layer configured to protect the barrier layer from oxidation phenomena, said trench being formed throughout the thickness of the protection layer and through at least part of the barrier layer, the sacrificial structure (28; 60) being formed on the protection layer, wherein the sacrificial structure (28; 60) comprises a photoresist layer (28; 60"), and the step of depositing said one or more metal layers (22a, 22b; 22) comprises using the photoresist layer (28; 60") as deposition mask, wherein the step of using the photoresist layer as deposition mask comprises shaping the photoresist layer in order to form a through-opening through the photoresist layer, said through-opening being delimited by tilted side walls conferring to the photoresist layer a truncated cone shape with a larger base at the protection layer, the tilted side walls being tilted with respect to a vertical direction, and wherein depositing one or more metal layers (22a, 22b; 22) in said trench is carried out substantially along said vertical direction, so that the projection of the tilted side walls allows formation of the one or more metal layers (22a, 22b; 22) in the trench that are not in direct contact with the tilted side walls, nor with the side walls of the underlying protection layer and barrier layer. - forming a sacrificial structure (28; 60) on a semiconductor body comprising a heterostructure; - forming, through the sacrificial structure (28; 60), an opening (35; 42), through which a surface region of the semiconductor body is exposed at said heterostructure; - etching the surface region of the semiconductor body using said sacrificial structure (28; 60) as etching mask to form a trench in the heterostructure; - depositing one or more metal layers (22a, 22b; 22) in said trench and on the sacrificial structure (28; 60); and - carrying out a lift-off process of the sacrificial structure (28; 60), wherein the semiconductor body comprises a substrate, a channel layer on the substrate, a barrier layer on the channel layer, and a protection layer on the barrier layer configured to protect the barrier layer from oxidation phenomena, said trench being formed throughout the thickness of the protection layer and through at least part of the barrier layer, the sacrificial structure (28; 60) being formed on the protection layer, wherein the sacrificial structure (28; 60) comprises a photoresist layer (28; 60"), and the step of depositing said one or more metal layers (22a, 22b; 22) comprises using the photoresist layer (28; 60") as deposition mask, wherein the step of using the photoresist layer as deposition mask comprises shaping the photoresist layer in order to form a through-opening through the photoresist layer, said through-opening being delimited by tilted side walls conferring to the photoresist layer a truncated cone shape with a larger base at the protection layer, the tilted side walls being tilted with respect to a vertical direction, and wherein depositing one or more metal layers (22a, 22b; 22) in said trench is carried out substantially along said vertical direction, so that the projection of the tilted side walls allows formation of the one or more metal layers (22a, 22b; 22) in the trench that are not in direct contact with the tilted side walls, nor with the side walls of the underlying protection layer and barrier layer.