Semiconductor device having deep wells and fabrication method thereof

Semiconductor devices and methods of fabricating the same are provided. An insulating film can be disposed on a semiconductor substrate, and insulating film patterns can be formed opening a plurality of areas with predetermined widths by patterning the insulating film. A plurality of ion implantation areas having a first conductivity type can be formed by implanting impurities into the plurality of open areas, and an oxide film pattern can be formed on each of the ion implantation areas. The insulating film patterns can be removed, and ion implantation areas having a second conductivity type can be formed by implanting impurities using the oxide film pattern as a mask. The semiconductor substrate can be annealed at a high temperature to form deep wells.