A device casing includes a wall having a metallic substrate and electrical connection of a feedthrough that includes a metal through-element made at least in a zone of isolation of the area of the feedthrough from the substrate material, in the form of an islet of closed contour, physically and electrically isolated from the substrate. An interface for coupling the through-element to the substrate provides the mechanical securing of the through-element to the substrate and the electrical isolation thereof and includes a peripheral lateral layer made of an electrically isolating material that surrounds the through-element over the whole periphery thereof and extends transversally through the thickness of the thinned area of the substrate. The substrate, the through-element and the lateral layer form a monolithically integrated unit, and the lateral layer provides essentially and directly both the mechanical securing and the electrical isolation between through-element and substrate.