Method for forming spacers of a gate of a field-effect transistor, the gate comprising edges and a top and being situated above a layer made of a semi-conductive material, at least one layer made of silicon oxide (SiO 2) forming a hard mask situated on the gate or forming an insulation trench, the method comprising a step of forming a dielectric layer covering the gate of the transistor, the method comprising: - after the step of forming the dielectric layer, at least one step of modifying said dielectric layer by bringing together the dielectric layer with a plasma creating a bombardment of anisotropic light ions according to a favoured direction parallel to the edges of the gate, the conditions of the plasma, in particular the energy from the light ions and the dose implanted being selected so as to modify, by implantation of light ions, at least portions of the dielectric layer which are situated on a top of the gate and on either side of the gate and which are perpendicular to the edges of the gate by conserving portions of the dielectric layer covering the edges of the gate, not modified or not modified over the whole of the thickness thereof; the light ions being hydrogen-based and/or helium-based (He) ions; - at least one step of removing the modified dielectric layer using a selective etching of said modified dielectric layer opposite the layer made of a semi-conductive material and opposite the non-modified dielectric layer; characterised in that the step of removing the modified dielectric layer comprises: - a dry etching carried out by bringing together a gaseous mixture, preferably only gaseous, comprising at least one first hydrofluoric acid-based component, the hydrofluoric acid transforming the modified dielectric layer into non-volatile residue at ambient temperature, said gaseous mixture having no proton-accepting groups, - only after the dry etching: a removal of the non-volatile residue at ambient temperature by a wet cleaning or by a thermal sublimation annealing. - after the step of forming the dielectric layer, at least one step of modifying said dielectric layer by bringing together the dielectric layer with a plasma creating a bombardment of anisotropic light ions according to a favoured direction parallel to the edges of the gate, the conditions of the plasma, in particular the energy from the light ions and the dose implanted being selected so as to modify, by implantation of light ions, at least portions of the dielectric layer which are situated on a top of the gate and on either side of the gate and which are perpendicular to the edges of the gate by conserving portions of the dielectric layer covering the edges of the gate, not modified or not modified over the whole of the thickness thereof; the light ions being hydrogen-based and/or helium-based (He) ions; - at least one step of removing the modified dielectric layer using a selective etching of said modified dielectric layer opposite the layer made of a semi-conductive material and opposite the non-modified dielectric layer; - a dry etching carried out by bringing together a gaseous mixture, preferably only gaseous, comprising at least one first hydrofluoric acid-based component, the hydrofluoric acid transforming the modified dielectric layer into non-volatile residue at ambient temperature, said gaseous mixture having no proton-accepting groups, - only after the dry etching: a removal of the non-volatile residue at ambient temperature by a wet cleaning or by a thermal sublimation annealing.