A method of fabricating a semiconductor device includes forming a mask pattern over a semiconductor substrate to define a channel region. A portion of the semiconductor substrate is etched using the mask pattern as an etching mask to form a first pillar. A spacer is formed over a sidewall of the mask pattern and the first pillar. A portion of the semiconductor substrate exposed between the first pillars is etched using the spacer and the mask pattern as an etching mask to form a second pillar elongated from the first pillar. A portion of the second pillar is selectively etched to form a third pillar. The spacer and the mask pattern are removed. An impurity is implanted into an upper part of the first pillar and the semiconductor substrate between the third pillars to form a source/drain region. A surrounding gate is formed over an outside of the third pillar.