A semiconductor device includes a semiconductor substrate having first and second regions therein, a first lower semiconductor pattern, which protrudes from the semiconductor substrate in the first region and extends in a first direction across the semiconductor substrate, and a first gate electrode, which extends across the first lower semiconductor pattern and the semiconductor substrate in a second direction. A plurality of semiconductor sheet patterns are provided, which are spaced apart from each other in a third direction to thereby define a vertical stack of semiconductor sheet patterns, on the first lower semiconductor pattern. A first gate insulating film is provided, which separates the plurality of semiconductor sheet patterns from the first gate electrode. A second lower semiconductor pattern is provided, which protrudes from the semiconductor substrate in the second region. A plurality of wire patterns are provided, which are spaced apart from each other on the second lower semiconductor pattern. A second gate insulating film is wrapped around each of the plurality of wire patterns.