Method for forming spacers (152a, 152b) of a gate of a field-effect transistor, the gate comprising a top and sides and being located above an active layer made of a semiconductor material, characterised in that it comprises: - at least one step of forming a protective layer covering the gate, the protective layer being a layer containing nitride and/or containing silicon (Si) and/or containing carbon that has a dielectric constant less than or equal to 8; - at least one step of modifying the protective layer by placing the protective layer in the presence of a plasma into which CxHy is introduced, where x is the proportion of carbon and y is the proportion of hydrogen, and comprising ions heavier than hydrogen; the conditions of the plasma, in particular the concentration of CxHy, the energy of the plasma ions and the main direction of implantation being chosen in such a way that: -- the plasma creates a bombardment of ions made from hydrogen (H, H +, H 2 +, H 3 +, etc.) from the CxHy, the bombardment being anisotropic in the main direction of implantation that is parallel to the sides of the gate, in such a way as to form a modified protective layer by modifying portions of the protective layer located on the top of the gate and on either side of the gate and in such a way as to preserve non-modified portions (152a, 152b) of the protective layer covering the sides of the gate, -- chemical species of the plasma containing carbon from the CxHy form a carbon film in particular on surfaces parallel to the main direction of implantation; -- the plasma creates a bombardment of the ions heavier than hydrogen that prevents said chemical species of the plasma containing carbon and coming from the CxHy from forming a carbon film in particular on the surfaces of the protective layer that are perpendicular to the main direction of implantation; - at least one step of removing the modified protective layer via selective etching of the modified protective layer with respect to the non-modified portions (152a, 152b) of the protective layer. - at least one step of forming a protective layer covering the gate, the protective layer being a layer containing nitride and/or containing silicon (Si) and/or containing carbon that has a dielectric constant less than or equal to 8; - at least one step of modifying the protective layer by placing the protective layer in the presence of a plasma into which CxHy is introduced, where x is the proportion of carbon and y is the proportion of hydrogen, and comprising ions heavier than hydrogen; the conditions of the plasma, in particular the concentration of CxHy, the energy of the plasma ions and the main direction of implantation being chosen in such a way that: -- the plasma creates a bombardment of ions made from hydrogen (H, H +, H 2 +, H 3 +, etc.) from the CxHy, the bombardment being anisotropic in the main direction of implantation that is parallel to the sides of the gate, in such a way as to form a modified protective layer by modifying portions of the protective layer located on the top of the gate and on either side of the gate and in such a way as to preserve non-modified portions (152a, 152b) of the protective layer covering the sides of the gate, -- chemical species of the plasma containing carbon from the CxHy form a carbon film in particular on surfaces parallel to the main direction of implantation; -- the plasma creates a bombardment of the ions heavier than hydrogen that prevents said chemical species of the plasma containing carbon and coming from the CxHy from forming a carbon film in particular on the surfaces of the protective layer that are perpendicular to the main direction of implantation; -- the plasma creates a bombardment of ions made from hydrogen (H, H +, H 2 +, H 3 +, etc.) from the CxHy, the bombardment being anisotropic in the main direction of implantation that is parallel to the sides of the gate, in such a way as to form a modified protective layer by modifying portions of the protective layer located on the top of the gate and on either side of the gate and in such a way as to preserve non-modified portions (152a, 152b) of the protective layer covering the sides of the gate, -- chemical species of the plasma containing carbon from the CxHy form a carbon film in particular on surfaces parallel to the main direction of implantation; -- the plasma creates a bombardment of the ions heavier than hydrogen that prevents said chemical species of the plasma containing carbon and coming from the CxHy from forming a carbon film in particular on the surfaces of the protective layer that are perpendicular to the main direction of implantation; - at least one step of removing the modified protective layer via selective etching of the modified protective layer with respect to the non-modified portions (152a, 152b) of the protective layer.