Method for forming spacers (152a, 152b) of a gate of a field-effect transistor, the gate having a top and sides and being situated above an active layer made of a semi-conductive material, the method comprising a step of forming a protective layer covering the gate of said transistor, the protective layer having a dielectric constant equal to or less than 8, the method being characterised in that it comprises, after the step of forming the protective layer; - at least one step of forming a carbon film on the transistor; - after the step of forming the carbon film, at least one step of removing the carbon film on the top of the gate and on either side of the gate by putting the carbon film in contact with a plasma creating a bombardment of ions heavier than hydrogen (H 2) ions along a main direction so as to remove at least portions of the carbon film situated on the top and either side of the gate and which are perpendicular to said main direction, by leaving in place residual portions (217a, 217b) of the carbon film at the level of the edges of the gate; - at least one step of modifying the protective layer by putting the protective layer in contact with a plasma comprising hydrogen-based (H, H +, H 2 +, H 3 +, etc.) and/or helium-based (He) ions and creating an anisotropic bombardment of hydrogen-based (H, H +, H 2 +, H 3 +, etc.) and/or helium-based (He) ions along said main direction which is parallel to edges of the gate, said bombardment being achieved so as to modify at least portions of the protective layer which are situated on the top and either side of the gate and which are perpendicular to the edges of the gate by preserving non-modified portions (152a, 152b) of the protective layer covering the edges of the gate; and - after the step of modifying the protective layer, the step of forming the carbon film and the step of removing portions of the carbon film leaving in place residual portions (217a, 217b) of the carbon film at the level of the edges of the gate, at least one step of removing the modified protective layer using an etching of the modified protective layer which is selective relative to non-modified portions (152a, 152b) of the protective layer and to opposite residual portions (217a, 217b) of the carbon film; and wherein the at least one step of forming the carbon film and the at least one step of modifying the protective layer are not simultaneously produced. - at least one step of forming a carbon film on the transistor; - after the step of forming the carbon film, at least one step of removing the carbon film on the top of the gate and on either side of the gate by putting the carbon film in contact with a plasma creating a bombardment of ions heavier than hydrogen (H 2) ions along a main direction so as to remove at least portions of the carbon film situated on the top and either side of the gate and which are perpendicular to said main direction, by leaving in place residual portions (217a, 217b) of the carbon film at the level of the edges of the gate; - at least one step of modifying the protective layer by putting the protective layer in contact with a plasma comprising hydrogen-based (H, H +, H 2 +, H 3 +, etc.) and/or helium-based (He) ions and creating an anisotropic bombardment of hydrogen-based (H, H +, H 2 +, H 3 +, etc.) and/or helium-based (He) ions along said main direction which is parallel to edges of the gate, said bombardment being achieved so as to modify at least portions of the protective layer which are situated on the top and either side of the gate and which are perpendicular to the edges of the gate by preserving non-modified portions (152a, 152b) of the protective layer covering the edges of the gate; and - after the step of modifying the protective layer, the step of forming the carbon film and the step of removing portions of the carbon film leaving in place residual portions (217a, 217b) of the carbon film at the level of the edges of the gate, at least one step of removing the modified protective layer using an etching of the modified protective layer which is selective relative to non-modified portions (152a, 152b) of the protective layer and to opposite residual portions (217a, 217b) of the carbon film;