A method is provided for forming spacers of a gate of a transistor, including: providing an active layer surmounted by a gate; forming a dielectric layer covering the gate and the active layer, the dielectric layer having lateral portions and basal portions; anisotropically modifying the basal portions by implantation of light ions, forming modified basal portions; and removing the modified basal portions by selective etching, so as to form the spacers on the lateral flanks of the gate from the unmodified lateral portions, in which, before the removing step, the anisotropic modification of the basal portions includes n successive implantation phases having implantation energies Γi (i=1 . . . n) which are distinct from each other, the n phases being configured to implant the light ions at different nominal implantation depths.