A semiconductor device includes a substrate including an active fin and an isolation layer thereon, a first gate structure on the active fin, the first gate structure including a first gate insulation layer pattern and a first metal pattern, and the first metal pattern having a first conductivity type and directly contacting the first gate insulation layer pattern, a first channel region at a portion of the active fin facing a bottom surface of the first gate structure, the first channel region including impurities having the first conductivity type, and first source/drain regions at upper portions of the active fin adjacent to opposite sidewalls of the first gate structure, the first source/drain regions including impurities having a second conductivity type different from the first conductivity type.