Provided is a semiconductor device comprising a substrate including a first area and a second area, first through third crystalline layers sequentially stacked on the first area and having first through third lattice constants, respectively, a first gate electrode formed on the third crystalline layer, fourth and fifth crystalline layers sequentially stacked on the second area and having fourth and fifth lattice constants, respectively, and a second gate electrode formed on the fifth crystalline layer, wherein the third lattice constant is greater than the second lattice constant, the second lattice constant is greater than the first lattice constant, and the fifth lattice constant is smaller than the fourth lattice constant.