The effect of the number and position of discrete dopants on device characteristics is crucial in determining the behavior of nanoscale semiconductor devices. We explore the fluctuations of threshold voltage (V th) roll-off in nanoscale bulk fin-type field effect transistors (FinFETs) by a three-dimensional (3D) statistically full-scale "atomistic" device simulation technique. The explored devices are of three different dimensions: 16, 22, and 30 nm3. Discrete dopants are statistically positioned into the 3D channel region to explore associated carrier transport characteristics, concurrently capturing "dopant concentration variation" and "dopant position fluctuation". For the device with a gate length of 16 nm, the Vth fluctuation of FinFETs is only half that of planar metal - oxide - semiconductor (MOS) FET. Compared with planar MOSFETs, the bulk FinEFTs can significantly suppress the fluctuation of Vth roll-off. The standard deviation of Vth is proportional to (WL)-25, which is better than the (WL) -0.5 of planar devices. The superior immunity against fluctuation and the stable fluctuation of Vth roll-off indicate the bulk FinFET to be a promising device for the sub-16 nm technology era.