A method for forming a
semiconductor structure. The method comprises: providing a substrate; forming a gate structure on the substrate; forming a threshold-
voltage-adjustment region in the substrate, wherein the threshold-
voltage-adjustment region has threshold-
voltage-adjusting ions; and forming a lightly doped drain region in the substrate, wherein the lightly doped drain region has light-
doping ions. Threshold-voltage-adjusting ions are implanted after a gate structure is formed, such that the threshold-voltage-adjusting ions have a deeper implantation depth outside a channel region. The implantation of light-
doping ions is performed after the implantation of the threshold-voltage-adjusting ions, and since the threshold-voltage-adjusting ions have a deeper implantation depth outside the channel region, the formation of deeper and more hierarchical junction depths in source-drain regions by the implanted light-
doping ions is thus facilitated, thereby alleviating the
hot carrier injection effect. During such procedure, it is not necessary to increase the implantation energy and annealing heat for the light-doping ions, thereby effectively reducing damage to the structure and performance of a device. Moreover, it is also not necessary to perform non-self-aligned masked
ion implantation, thereby effectively simplifying the process.