In described examples an integrated circuit (IC) has multiple layers of dielectric material overlying at least a portion of a surface of a substrate. A trench is etched through the layers of dielectric material to expose a portion the substrate to form a trench floor, the trench being surrounded by a trench wall formed by the layers of dielectric material. A metal perimeter band surrounds the trench adjacent the trench wall, the perimeter band being embedded in one of the layers of the dielectric material.