A semiconductor device and a method for fabricating the same are provided. A semiconductor device having a substrate can include a lower semiconductor layer, an upper semiconductor layer on the lower semiconductor layer, and a buried insulating layer between the lower semiconductor layer and the upper semiconductor layer. A first trench can be in the upper semiconductor layer having a lowest surface above the buried insulating layer and a first conductive pattern recessed in the first trench. A second trench can be in the lower semiconductor layer, the buried insulating layer, and the upper semiconductor layer. A second conductive pattern can be in the second trench and a first source/drain region can be in the upper semiconductor layer between the first conductive pattern and the second conductive pattern.