Method for forming, on a single substrate of the semiconductor on insulator type or fully depleted semiconductor on insulator (FDSOI) type, at least one first transistor and at least one second transistor, the method comprising at least the following steps of: - Forming, on a substrate, at least one first gate pattern and at least one second gate pattern; - Depositing, on the first and second gate patterns (200, 300) at least: • a first protective layer, • a second protective layer overlaying the first protective layer and made of a material that is different from that of the first protective layer, • a third protective layer overlaid by the first protective layer and by the second protective layer, the third protective layer being made of a material that allows the material of the first protective layer to be selectively etched relative to the material of the third protective layer; and the second protective layer and the third protective layer are each made of a material selected from among the following materials: silicon nitride (SiN), materials whose dielectric constant k is less than 7, SiCO, SiC, SiCN, SiOCN, SiCBN; - Masking the second gate pattern by a masking layer; - Isotropic etching of the second protective layer located on the first gate pattern, so as to completely remove the second protective layer located on the first gate pattern, while preserving the first protective layer on the first gate pattern, the second gate pattern being masked by the masking layer during this isotropic etching; - Removing the masking layer after the isotropic etching step; - Before the masking step or after the step of removing the masking layer: selective anisotropic etching of the second protective layer relative to the first protective layer, so as to at least partially remove the second protective layer located on a top of the second gate pattern and so as to preserve at least a part of the thickness of the second protective layer located on the sidewalls of the second gate pattern; - Before the step of depositing the first and the second protective layers (500, 600), a step of depositing, on the first and second gate patterns (200, 300), the third protective layer disposed beneath the first protective layer and covering the first and second gate patterns (200, 300); - After the selective anisotropic etching of the second protective layer relative to the first protective layer: a step of selectively etching the first protective layer relative to the third protective layer so as to completely remove the first protective layer from the first gate pattern and so as to preserve the third protective layer. - Forming, on a substrate, at least one first gate pattern and at least one second gate pattern; - Depositing, on the first and second gate patterns (200, 300) at least: • a first protective layer, • a second protective layer overlaying the first protective layer and made of a material that is different from that of the first protective layer, • a third protective layer overlaid by the first protective layer and by the second protective layer, the third protective layer being made of a material that allows the material of the first protective layer to be selectively etched relative to the material of the third protective layer; and • a first protective layer, • a second protective layer overlaying the first protective layer and made of a material that is different from that of the first protective layer, • a third protective layer overlaid by the first protective layer and by the second protective layer, the third protective layer being made of a material that allows the material of the first protective layer to be selectively etched relative to the material of the third protective layer; and - Masking the second gate pattern by a masking layer; - Isotropic etching of the second protective layer located on the first gate pattern, so as to completely remove the second protective layer located on the first gate pattern, while preserving the first protective layer on the first gate pattern, the second gate pattern being masked by the masking layer during this isotropic etching; - Removing the masking layer after the isotropic etching step; - Before the masking step or after the step of removing the masking layer: selective anisotropic etching of the second protective layer relative to the first protective layer, so as to at least partially remove the second protective layer located on a top of the second gate pattern and so as to preserve at least a part of the thickness of the second protective layer located on the sidewalls of the second gate pattern; - Before the step of depositing the first and the second protective layers (500, 600), a step of depositing, on the first and second gate patterns (200, 300), the third protective layer disposed beneath the first protective layer and covering the first and second gate patterns (200, 300); - After the selective anisotropic etching of the second protective layer relative to the first protective layer: a step of selectively etching the first protective layer relative to the third protective layer so as to completely remove the first protective layer from the first gate pattern and so as to preserve the third protective layer.