This paper investigates emerging capacitor technologies to address the need of high power density (e.g.greater than 1W/mm²) DC-DC switching converters. Existing modeling of DC-DC step-down switched capacitor converter (SCC) is employed in this work to benchmark different types of capacitors, such as standard MOS capacitor and emerging silicon capacitors. Two different silicon process dies assemblycalled 3D-SCC is introduced to benefit from higher performance of advanced deep-trench capacitors (DTC) compared to native CMOS capacitors. Simulations quantify the power density gain e.g. 8W/mm² vs 0.08W/mm² for 3D-SCC and 2D-MOS SCC at 80% efficiency, respectively. Finally, design guidelines to optimize capacitor parameters are given to improve the capacitor design to be adopted in 3D-SCC.