Provided are a semiconductor device and a method for fabricating the same. The semiconductor device includes a lower fin that protrudes from a substrate and extends in a first direction, an oxide film the lower fin, an upper fin that protrudes from the oxide film and that is spaced apart from the lower fin at a position corresponding to the lower fin, and a gate structure the upper fin that extends in a second direction to intersect the upper fin, wherein germanium (Ge) is included in a portion of the oxide film located between the lower fin and the upper fin.