A method of fabricating a semiconductor device includes providing a substrate including a semiconductor material having a first lattice constant and then patterning the substrate to form a first semiconductor pattern extending in a first direction. A second semiconductor pattern is also formed on and in contact with the first semiconductor pattern. The second semiconductor pattern extends in the first direction and has a second lattice constant that is sufficiently greater than the first lattice constant so that lattice stress is present at an interface between the first semiconductor pattern and the second semiconductor pattern. The second semiconductor pattern is further patterned to define a sidewall of the second semiconductor pattern that extends in a second direction intersecting the first direction. A gate electrode is formed, which extends in the first direction on the second semiconductor pattern.