Vertical memory devices

A vertical memory device, comprising:

• a substrate including a first region which is a cell array region and a second region surrounding the first region;
• gate electrodes stacked on the substrate to be spaced apart from each other in a first direction vertical to an upper surface of the substrate, each of the gate electrodes extending in a second direction parallel to the upper surface of the substrate and including a pad at an end portion thereof in the second direction;
• a channel extending through the gate electrodes in the first direction on the first region of the substrate;
• and
• contact plugs extending in the first direction on the second region of the substrate to contact the pads of the gate electrodes respectively,
• wherein edge portions in the second direction of first pads among the pads, in a plan view, are convex in a direction away from the first region, and the first pads are arranged in a third direction parallel to the upper surface of the substrate and orthogonal to the second direction.

A vertical memory device, comprising:

• a substrate including a first region which is a cell array region and a second region surrounding the first region;
• gate electrodes stacked on the substrate to be spaced apart from each other in a first direction vertical to an upper surface of the substrate, each of the gate electrodes extending in a second direction parallel to the upper surface of the substrate and including a pad being at an end portion thereof in the second direction;
• a channel extending through the gate electrodes in the first direction on the first region of the substrate;
• and
• contact plugs extending in the first direction on the second region of the substrate to contact the pads of the gate electrodes respectively,
• wherein a boundary of edge portions in the second direction of first pads among the pads, in a plan view, has a first curved shape that is convex in a direction away from the first region of the substrate, the first pads being arranged in a third direction parallel to the upper surface of the substrate and orthogonal to the second direction,
• wherein a boundary of edge portions in the second direction of second pads among the pads, in a plan view, has a second curved shape that is convex in the direction away from the first region of the substrate, the second pads being formed on the first pads and arranged in the third direction, and
• wherein a curvature of the second curved shape is less than a curvature of the first curved shape.