Continued challenge for higher-performance semiconductor device requires the controlled doping of single-dopant atom to control the electrical properties1-10. Here we report the fabrication of semiconductors with both dopant number and position controlled by using a one-by-one doping technique, which we call "single-ion implantation (SII)" 11-19. This technique enables us to implant dopant ions one-by-one into a fine semiconductor region until the necessary number is reached. Electrical measurements reveal that the threshold voltage (Vth) fluctuation for the ordered dopant arrays is less than for conventional random doping. We also find that the device with ordered dopant array exhibits two times the lower average value (-0.4V) of Vth shift than the random dopant distribution (-0.2V). We conclude that the observed lower value originates from the uniformity of electrostatic potential in the channel region due to the ordered distribution of dopant atoms. The ordered dopant arrays may increase the prospects of fluctuation-controlled advanced silicon transistors.