Semiconductor device including overlay key structure

A semiconductor device comprising:

• a mold on an overlay key region of a substrate, the mold having insulation layers and sacrificial layers alternately and repeatedly stacked in a first direction perpendicular to an upper surface of the substrate;
• and
• a pair of lower overlay key structures disposed in a second direction parallel to the upper surface of the substrate, each of the pair of lower overlay key structures at least partially penetrating through the mold;
• and
• a pair of upper overlay key structures disposed in the second direction, corresponding to the pair of lower overlay key structures, respectively, each of the upper overlay key structures being on the mold,
• wherein:
• the pair of lower overlay key structures include a first lower overlay key structure and a second lower overlay key structure,
• the first lower overlay key structure includes a first lower overlay key group and a second lower overlay key group,
• the first lower overlay key group includes first, second, third and fourth lower overlay key sub-groups disposed having 90-degree rotational symmetry in a clockwise direction about a first center point,
• the second lower overlay key group includes fifth, sixth, seventh and eighth lower overlay key sub-groups having 90-degree rotational symmetry in the clockwise direction about a second center point,
• the first to fourth lower overlay key sub-groups are radially arranged to be spaced apart from the first center point by a first distance, and
• the fifth to eighth lower overlay key sub-groups are radially arranged to be spaced apart from the second center point by a second distance less than the first distance.

A semiconductor device comprising:

• a substrate including shot regions, each of the shot regions including a reference shot area and a double exposure area;
• a first mold on the double exposure area of the substrate, the first mold having first insulation layers and first sacrificial layers alternately and repeatedly stacked in a first direction perpendicular to an upper surface of the substrate;
• a first pair of overlay key structures, each of the first pair of overlay key structures including a first lower overlay key structure and a first upper overlay key structure, the first lower overlay key structure at least partially penetrating through the first mold, and the first upper overlay key structure being on the first lower overlay key structure;
• a second mold on the reference shot area of the substrate, the second mold having second insulation layers and second sacrificial layers alternately and repeatedly stacked in the first direction;
• and
• a second pair of overlay key structures, each of the second pair of overlay key structures including a second lower overlay key structure and a second upper overlay key structure, the second lower overlay key structure at least partially penetrating through the second mold, and the second upper overlay key structure being on the second lower overlay key structure.