In a semiconductor device, the semiconductor device may include a first active structure, a first gate insulation layer, a first gate electrode, a first impurity region, a second impurity region and a contact structure. The first active structure may include a first lower pattern in a first region of a substrate and a first upper pattern on the first lower pattern. The first gate insulation layer may be formed on a sidewall of the first upper pattern. The first gate electrode may be formed on the first gate insulation layer. The first impurity region may be formed in the first lower pattern. The second impurity region may be formed in the first upper pattern. The contact structure may surround an upper surface and an upper sidewall of the first upper pattern including the second impurity region. Accordingly, the contact resistance between the contact structure and the second impurity region may be decreased and structural stability of the contact structure may be improved.