The invention concerns the field of micromechanical parts, in particular, for timepiece movements. The invention relates to a method of fabricating a mold that includes the following steps: (a) providing a substrate that has a top layer and a bottom layer made of electrically conductive, micromachinable material, and secured to each other by an electrically insulating, intermediate layer; (b) etching at least one pattern in the top layer as far as the intermediate layer to form at least one cavity in the mold; (c) coating the top part of the substrate with an electrically insulating coating; and (d) directionally etching the coating and the intermediate layer to limit the presence thereof exclusively at each vertical wall formed in the top layer.