The through-silicon via (TSV) structure with enhanced capacitance is proposed for the power distribution network in 3D ICs, where an n+ contact on the top surface surrounding the oxide-silicon interface of the power TSV is used, instead of a p-substrate. The n+ contact supplies the majority carrier to the channel, so the inversion layer can be formed at high frequencies. Since power TSVs are always biased to a voltage higher than the threshold voltage, changing the depletion layer to an inversion layer enables the larger capacitance in the proposed TSV. The voltage and frequency characteristics of the proposed TSV structure are simulated and compared with the conventional structure. In addition, a model based on RC transmission line is proposed to estimate the capacitance degeneration at high frequencies. The model showed a good match with simulated results over a wide frequency range.