In a semiconductor device, the semiconductor device includes a conductive structure, first insulating layers and first conductive layer patterns. The conductive structure includes a first portion, second portions and third portions. The second portions extend in a first direction on the first portion. The second portions are spaced apart from one another in a second direction substantially perpendicular to the first direction. The third portions are provided on the second portions. The third portions are spaced apart from one another in the first and second directions. The first insulating layers cover sidewalls of the second portions. The first conductive layer patterns are provided on the first insulating layers.