Semiconductor devices

A semiconductor device comprising:

• a substrate comprising a cell array region and a connection region;
• a stack structure comprising a plurality of conductive layers stacked on the substrate, a first one of the plurality of conductive layers comprising a pad region that protrudes relative to an overlying second one of the plurality of conductive layers on the connection region;
• a vertical structure on the cell array region and penetrating the stack structure;
• a plurality of support structures penetrating the pad region, the plurality of support structures each adjacent to an edge of the pad region;
• and
• a contact plug connected with a center of the pad region,
• wherein a first shape of a first portion of the plurality of support structures in a first plane is different from a second shape of a second portion of the plurality of support structures in a second plane, and the first plane and the second plane are parallel to an upper surface of the substrate, and
• wherein, in a horizontal cross-sectional view, the first shape of the first portion of the plurality of support structures in the first plane comprises an elliptical shape comprising a major axis that intersects a first direction that is toward the contact plug.