In this work, we conducted Capacitance-Voltage (C-V) measurement on an inverted Metal-Oxide-Semiconductor (MOS) structure device with in-situ Boron (B) doped silicon quantum dot (QD) materials as the semiconductor layer. The highly conductive P++ Si (0.001-0.005 ohmic.cm) and thermal oxide worked as the metallic gate and the dielectric layer respectively in this MOS structure. We demonstrated that there were less parasitic components in the inverted MOS in vertical structure than MOS in lateral structure. C-V curves showed clear accumulation, depletion and inversion regions as well as a frequency dispersion effect. An analysis on the equivalent circuit model and material electrical properties was presented to explain the frequency dispersion effect. We propose that the frequency dependent shift could be eliminated by removing the frequency-dependent capacitor component (Cm) in series with the ideal MOS equivalent circuit. This capacitor is possibly due to the long dielectric relaxation time in the Si QD material due to the high density of deep defects and the high resistivity. The estimated average doping level extracted from corrected C-V curves is high despite high resistivity.