Provided are semiconductor devices and methods of manufacturing the same. The semiconductor device includes a substrate including a first top surface, a second top surface lower in level than the first top surface, and a first perpendicular surface disposed between the first and second top surfaces, a first source/drain region formed under the first top surface, a first nanowire extended from the first perpendicular surface in one direction and being spaced apart from the second top surface, a second nanowire extended from a side surface of the first nanowire in the one direction, being spaced apart from the second top surface, and including a second source/drain region, a gate electrode on the first nanowire, and a dielectric layer between the first nanowire and the gate electrode.