A semiconductor device may include active pattern, a silicon liner, an insulation layer, an isolation pattern and a transistor. The active pattern may protrude from a substrate. The silicon liner having a crystalline structure may be formed conformally on surfaces of the active pattern and the substrate. The insulation layer may be formed on the silicon liner. The isolation pattern may be formed on the insulation layer to fill a trench adjacent to the active pattern. The transistor may include a gate structure and impurity regions. The gate structure may be disposed on the silicon liner, and the impurity regions may be formed at the silicon liner and the active pattern adjacent to both sides of the gate structure.