A semiconductor device manufacturing method is presented. The manufacturing method includes providing a semiconductor structure, comprising: a substrate, a plurality of semiconductor fins comprising a first semiconductor fin and a second semiconductor fin on the substrate, a plurality of trenches surrounding the semiconductor fins, and a first insulation layer filling the trenches; conducting a first doping process in the first semiconductor fin to form a first anti-punch-through region therein; removing at least a portion of the first insulation layer from the trenches; forming a second insulation layer filling a portion of the trenches not filled by the first insulation layer; and conducting a second doping process in the second semiconductor fin to form a second anti-punch-through region therein. This inventive concept reduces the chance of a dopant in the first doping process diffusing into the second semiconductor fin.