The application refers to an improved through silicon via including multi-material fill. An apparatus includes a substrate having at least one via disposed in the substrate, wherein the substrate includes a trench having a substantially trapezoidal cross-section, the trench extending through the substrate between a lower surface of the substrate and an upper surface of the substrate, wherein the top of the trench opens to a top opening, and the bottom of the trench opens to a bottom opening, the top opening being larger than the bottom opening. The apparatus can include a mouth surrounding the top opening and extending between the upper surface and the top opening, wherein a mouth opening in the upper surface is larger than the top opening of the trench, wherein the via includes a dielectric layer disposed on an inside surface of a trench. The apparatus includes and a fill disposed in the trench, with the dielectric layer sandwiched between the fill and the substrate.