Provided are a semiconductor device and a method of fabricating the semiconductor device. The semiconductor device can provide a trench MOS transistor having an up-drain structure. The semiconductor device can include a first conductive type well in a semiconductor substrate, a second conductive type well on the first conductive type well, trenches formed by removing portions of the second conductive type well and the first conductive type well; gates provided in the trenches with a gate dielectric being between each gate and the walls of the trench, a first conductive type source region and a second conductive type body region on the second conductive type well, the first conductive type source region surrounding a lateral surface of the gate, and a common drain between the gates, the common drain being connected to the first conductive type well.