The invention relates to a method of forming a layer of elastically unstrained crystalline material intended for electronics, optics, or optronics applications, wherein the method is carried out using a structure that includes a first crystalline layer which is elastically strained under tension (or respectively in compression) and a second crystalline layer which is elastically strained in compression (or respectively under tension), with the second layer being adjacent to the first layer. The method includes a step of diffusion between the two layers so that the differences between the respective compositions of the two layers is progressively reduced until they are substantially the same, so that the two layers then form just a single final layer of crystalline material having a composition which, in aggregate, is uniform, and wherein the respective compositions, thicknesses, and degrees of strain of the two layers are initially selected so that, after diffusion, the material then constituting the final layer no longer, in aggregate, exhibits elastic strain. The diffusion can be accomplished by heat treating the structure.