A method is used to prepare the remainder of a donor substrate, from which a layer has been removed by delamination in a plane weakened by ion implantation. The remainder comprises, on a main face, an annular step corresponding to a non-removed part of the donor substrate. The method comprises the deposition of a smoothing oxide on the main face of the remainder in order to fill the inner space defined by the annular step and to cover at least part of the annular step, as well as heat treatment for densification of the smoothing oxide. A substrate is produced by the method, and the substrate may be used in subsequent processes.