A method for forming a wire in a layer based on a monocrystalline or amorphous material. The method forms two trenches in the layer, crossing through one face of the layer, separated from each other by one portion of the layer, by an etching of the layer on which is arranged an etching mask, and anneals, under hydrogenated atmosphere, the layer, the etching mask being maintained on the layer during the annealing. The depths and widths of the sections of the two trenches, and the width of a section of the portion of the layer, are such that the annealing eliminates a part of the portion of the layer, the two trenches then forming a single trench in which a remaining part of the portion of the layer forms the wire.