A semiconductor device includes a substrate including a first part and a second part, a memory cell disposed on the first part, an insulation layer disposed on the first part and the second part, the insulation layer covering the memory cell, a portion of the insulation layer on the second part including a stepped sidewall, and a first pattern group disposed on the second part and in the portion of the insulation layer and the substrate. A first sidewall of the semiconductor device corresponds to the stepped sidewall including an upper sidewall, a lower sidewall and a connecting surface connecting the upper sidewall to the lower sidewall. The lower sidewall disposed under the upper sidewall is closer to the substrate than the upper sidewall, and has surface roughness different from surface roughness of the upper sidewall.