This work, for the first time, estimates the random dopant fluctuation (RDF) on DC characteristics of trapezoidal bulk FinFET devices by using an experimentally calibrated 3D quantum-mechanically corrected device simulation. For bulk FinFET devices under the same channel volume, we analyze the impact of geometry variation and RDF on the threshold voltage, the on-/off-state current with respect to different channel fin angles. The channel fin angle increases, the on-state current increases owing to increase of total fin width, but small- and large-fin-angle devices have comparable RDF. The threshold voltage is affected to different extents by RDs appearing in the upper and lower channel fin regions. Two major factors, the total fin width and the RD's position, affecting the Vth fluctuation of RDF are discussed.