A semiconductor device includes a substrate having a first region and a second region; a first nanowire in the first region in a direction perpendicular to an upper surface of the substrate; a second nanowire in the second region in a direction perpendicular to the upper surface of the substrate and having a height less than that of the first nanowire; first source/drain regions at top portion and bottom portion of the first nanowire; second source/drain regions at top portion and bottom portion of the second nanowire; a first gate electrode surrounding the first nanowire between the first source/drain regions; and a second gate electrode surrounding the second nanowire between the second source/drain regions.