A vertical power component includes a silicon substrate of a first conductivity type with a well of the second conductivity type on a lower surface of the substrate. The first well is bordered at a component periphery with an insulating porous silicon ring. An upper surface of the porous silicon ring is only in contact with the substrate of the first conductivity type. The insulating porous silicon ring penetrates into the substrate down to a depth greater than a thickness of the well. The porous silicon ring is produced by forming a doped well in a first surface of a doped substrate, placing that first surface of the substrate into an electrolytic bath, and circulating a current between an opposite second surface of the substrate and the electrolytic bath.