Through silicon via including multi-material fill

An apparatus comprising:

• a substrate including at least one via disposed in the substrate, wherein the substrate comprises:
• 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;
• and
• 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,
• a second substrate bonded to the substrate;
• wherein the via comprises:
• a dielectric layer disposed on an inside surface of a trench;
• and
• a fill disposed in the trench, with the dielectric layer sandwiched between the fill and the substrate,
• wherein the trench defines a circuit in the substrate, with an inner portion of the substrate being in the circuit, and an outer portion surrounding the circuit,
• wherein the second substrate includes a sense capacitor, wherein one electrode is formed by a device substrate connected through a conductive substrate bond to a first contact coupled to the inner portion and another electrode is formed by a second contact coupled to the outer portion.