A semiconductor device may include a bit line extending in a first direction, a semiconductor pattern on the bit line, the semiconductor pattern including first and second vertical portions, which are opposite to each other in the first direction, and a horizontal portion connecting the first and second vertical portions, first and second word lines on the horizontal portion to be adjacent to the first and second vertical portions, respectively, and a gate insulating pattern between the first vertical portion and the first word line and between the second vertical portion and the second word line. A bottom surface of the horizontal portion may be located at a height that is lower than or equal to the uppermost surface of the bit line.