Abstract: A method of forming an implantation-induced isolation in a semiconductor substrate. First, an ion-implantation mask, such as a photoresist mask or a hard mask made of silicon nitride is defined on the semiconductor substrate to cover the active region. Second, oxygen ions are implanted into the semiconductor substrate to form an oxygen doping region for formation of the implantation-induced isolation. Third, a thermal annealing is used so that an isolating structure serving as the implantation-induced isolation is generated by reaction of the oxygen ions in the oxygen doping region with the component of the semiconductor substrate.