One of 3-D devices to achieve high density arrays was adopted in this study, where source and drain junctions are formed along the silicon fin. The screening by adjacent high fins for large sensing margin makes it hard to ion-implant with high angle so that vertical ion implantation is inevitable. In this study, the dependency of current characteristics on doping profiles is investigated by 3-D numerical analysis. The position of concentration peak and the doping gradient are varied to look into the effects on driving currents. Through these analyses, the optimum condition of ion implantation for 3-D devices is estimated.