A semiconductor device includes an epitaxy layer formed on semiconductor substrate, a device layer formed on the epitaxy layer, a trench formed within the semiconductor substrate and including a dielectric layer forming a liner within the trench and a conductive core forming a through-silicon via conductor, and a deep trench isolation structure formed within the substrate and surrounding the through-silicon via conductor. A region of the epitaxy layer formed between the through-silicon via conductor and the deep trench isolation structure is electrically isolated from any signals applied to the semiconductor device, thereby decreasing parasitic capacitance.