A semiconductor device includes a stack structure including first electrodes and insulating layers alternately stacked on each other, a second electrode passing through the stack structure, and variable resistance patterns each interposed between the second electrode and a corresponding one of the first electrodes. Each of the first electrodes includes a first sidewall facing the second electrode, and each of the insulating layers includes a second sidewall facing the second electrode. At least a part of each of the variable resistance patterns protrudes farther towards the second electrode than the second sidewall.