According to example embodiments, a vertical type semiconductor device includes a pillar structure on a substrate. The pillar structure includes a semiconductor pattern and a channel pattern. The semiconductor pattern includes an impurity region. A first word line structure faces the channel pattern and is horizontally extended while surrounding the pillar structure. A second word line structure has one side facing the impurity region of the semiconductor pattern and another side facing the substrate. A common source line is provided at a substrate portion adjacent to a sidewall end portion of the second word line structure.