Semiconductor devices

Abstract

A semiconductor device includes a gate electrode structure, a memory channel structure, and first and second contact plugs. The gate electrode structure includes gate electrodes spaced apart from each other in a first direction, and each of the gate electrodes extends in a second direction. The gate electrode structure has a staircase shape including step layers each of which includes two gate electrodes. The memory channel structure extends through the gate electrode structure. The first contact plug contacts an upper surface of a first gate electrode of the two gate electrodes at an upper level in a corresponding step layer. The second contact plug contacts a sidewall of a second gate electrode of the two gate electrodes at a lower level in the corresponding step layer. The second contact plug extends in the first direction and is electrically insulated from gate electrodes disposed below the second gate electrode.