A method for making contact openings for connecting a field effect transistor from a stack of layers comprising at least an active layer made of a semi-conductor material, a silicide layer on the top of the active layer, a nitride-based layer on the top of the silicide layer and an electrically insulating layer on the top of the nitride-based layer, the method comprising the following steps: - a step of opening the insulating layer for forming in the insulating layer at least an opening exposing the nitride-based layer and delimited by flanks of the insulating layer; - a step of removing the nitride-based layer at the opening so as to expose the silicide layer; with the method being characterized in that the step of removing the nitride-based layer at the opening comprises the following steps: - at least a step of modifying the nitride-based layer at the opening by putting in contact the nitride-based layer with a plasma wherein CxHy is introduced where x is the proportion of carbon and y is the proportion of hydrogen ions, with the plasma comprising at least hydrogen-based ions (H, H +, H 2 +, H 3 + etc.) more particularly provided by CxHy, chemical species containing carbon provided by CxHy and ions heavier than hydrogen; the conditions of plasma, more particularly the concentration of CxHy, the ion energy and the main implantation direction being so chosen that: o at least a part of hydrogen-based ions provided by CxHy are implanted in a portion of the nitride-based layer at the opening and thus forming a modified portion of the nitride-based layer; o at least a part of the plasma chemical species containing carbon provided by CxHy form a carbon film on said flanks of the insulating layer; o the ions heavier than hydrogen prevent said carbon-containing plasma chemical species from forming a carbon film at the bottom of the opening, - at least a step of removing the modified portion of the nitride-based layer using a selective etching of the nitride-based modified portion relative to non-modified portions of the nitride-based layer and relative to the carbon film. - a step of opening the insulating layer for forming in the insulating layer at least an opening exposing the nitride-based layer and delimited by flanks of the insulating layer; - a step of removing the nitride-based layer at the opening so as to expose the silicide layer; with the method being characterized in that the step of removing the nitride-based layer at the opening comprises the following steps: - at least a step of modifying the nitride-based layer at the opening by putting in contact the nitride-based layer with a plasma wherein CxHy is introduced where x is the proportion of carbon and y is the proportion of hydrogen ions, with the plasma comprising at least hydrogen-based ions (H, H +, H 2 +, H 3 + etc.) more particularly provided by CxHy, chemical species containing carbon provided by CxHy and ions heavier than hydrogen; the conditions of plasma, more particularly the concentration of CxHy, the ion energy and the main implantation direction being so chosen that: o at least a part of hydrogen-based ions provided by CxHy are implanted in a portion of the nitride-based layer at the opening and thus forming a modified portion of the nitride-based layer; o at least a part of the plasma chemical species containing carbon provided by CxHy form a carbon film on said flanks of the insulating layer; o the ions heavier than hydrogen prevent said carbon-containing plasma chemical species from forming a carbon film at the bottom of the opening, - at least a step of removing the modified portion of the nitride-based layer using a selective etching of the nitride-based modified portion relative to non-modified portions of the nitride-based layer and relative to the carbon film. - at least a step of modifying the nitride-based layer at the opening by putting in contact the nitride-based layer with a plasma wherein CxHy is introduced where x is the proportion of carbon and y is the proportion of hydrogen ions, with the plasma comprising at least hydrogen-based ions (H, H +, H 2 +, H 3 + etc.) more particularly provided by CxHy, chemical species containing carbon provided by CxHy and ions heavier than hydrogen; the conditions of plasma, more particularly the concentration of CxHy, the ion energy and the main implantation direction being so chosen that: o at least a part of hydrogen-based ions provided by CxHy are implanted in a portion of the nitride-based layer at the opening and thus forming a modified portion of the nitride-based layer; o at least a part of the plasma chemical species containing carbon provided by CxHy form a carbon film on said flanks of the insulating layer; o the ions heavier than hydrogen prevent said carbon-containing plasma chemical species from forming a carbon film at the bottom of the opening, o at least a part of hydrogen-based ions provided by CxHy are implanted in a portion of the nitride-based layer at the opening and thus forming a modified portion of the nitride-based layer; o at least a part of the plasma chemical species containing carbon provided by CxHy form a carbon film on said flanks of the insulating layer; o the ions heavier than hydrogen prevent said carbon-containing plasma chemical species from forming a carbon film at the bottom of the opening, - at least a step of removing the modified portion of the nitride-based layer using a selective etching of the nitride-based modified portion relative to non-modified portions of the nitride-based layer and relative to the carbon film.