A method for etching a dielectric layer covering at least one top and at least one side (32, 32) of a structure preferably based on a semiconductor material, characterised by the fact that it comprises a plurality of sequences each comprising at least the following successive steps: - a first etching of the dielectric layer, by plasma, using a chemistry comprising at least: ∘ at least one first compound, the first compound being based on fluorine, and originating from the dissociation of at least one compound taken from fluorocarbon compounds and ∘ at least one second compound made from at least one silicon-based gas and taken from Si w Cl (2w+2) and Si w F (2w+2) w being a non-zero integer, ∘ oxygen. the first etching being carried out so as to: ∘ generate an ion bombardment mainly directed in a direction parallel to said side (32, 32), ∘ regulate the amount of the at least one first compound to consume all the fluorine-based compound during this first etching so as to interrupt the first etching before consuming the entire thickness of the dielectric layer located on the side and after having consumed the entire thickness of the dielectric layer located on the top, ∘ form a first protection layer by oxidation of an upper portion of the top of the structure made of a semiconductor material and form a second protection layer by oxidation of an upper portion of the dielectric layer located on the side, the thickness (e 50a) of the first protection layer being greater than the thickness (e 60a) of the second protection layer, - a second etching to completely remove the second protection layer while retaining a portion e 50b of the thickness of the first protection layer, the sequence being repeated until completely removing the dielectric layer located on the side of the structure. - a first etching of the dielectric layer, by plasma, using a chemistry comprising at least: ∘ at least one first compound, the first compound being based on fluorine, and originating from the dissociation of at least one compound taken from fluorocarbon compounds and ∘ at least one second compound made from at least one silicon-based gas and taken from Si w Cl (2w+2) and Si w F (2w+2) w being a non-zero integer, ∘ oxygen. the first etching being carried out so as to: ∘ generate an ion bombardment mainly directed in a direction parallel to said side (32, 32), ∘ regulate the amount of the at least one first compound to consume all the fluorine-based compound during this first etching so as to interrupt the first etching before consuming the entire thickness of the dielectric layer located on the side and after having consumed the entire thickness of the dielectric layer located on the top, ∘ form a first protection layer by oxidation of an upper portion of the top of the structure made of a semiconductor material and form a second protection layer by oxidation of an upper portion of the dielectric layer located on the side, the thickness (e 50a) of the first protection layer being greater than the thickness (e 60a) of the second protection layer, ∘ at least one first compound, the first compound being based on fluorine, and originating from the dissociation of at least one compound taken from fluorocarbon compounds and ∘ at least one second compound made from at least one silicon-based gas and taken from Si w Cl (2w+2) and Si w F (2w+2) w being a non-zero integer, ∘ oxygen. ∘ generate an ion bombardment mainly directed in a direction parallel to said side (32, 32), ∘ regulate the amount of the at least one first compound to consume all the fluorine-based compound during this first etching so as to interrupt the first etching before consuming the entire thickness of the dielectric layer located on the side and after having consumed the entire thickness of the dielectric layer located on the top, ∘ form a first protection layer by oxidation of an upper portion of the top of the structure made of a semiconductor material and form a second protection layer by oxidation of an upper portion of the dielectric layer located on the side, the thickness (e 50a) of the first protection layer being greater than the thickness (e 60a) of the second protection layer, - a second etching to completely remove the second protection layer while retaining a portion e 50b of the thickness of the first protection layer,