Three-dimensional (3D) semiconductor memory devices and methods of manufacturing the same

A three-dimensional (3D) semiconductor memory device comprising:

• a substrate comprising a cell array region and a connection region;
• and
• an electrode structure extending from the cell array region onto the connection region in a first direction, the electrode structure comprising a plurality of stack structures vertically stacked on the substrate to comprise a first stair step structure extending in the first direction, each of the plurality of stack structures comprising a plurality of electrodes vertically stacked to comprise a second stair step structure extending in a second direction that is substantially perpendicular to the first direction,
• wherein the substrate comprises a recessed portion adjacent to the electrode structure on the connection region.

A three-dimensional (3D) semiconductor memory device comprising:

• a substrate including first and second connection regions and a cell array region between the first and second connection regions in a first direction;
• and
• first and second electrode structures extending in the first direction and spaced apart from each other in a second direction that is substantially perpendicular to the first direction, each of the first and second electrode structures comprises a plurality of stack structures vertically stacked on the substrate to comprise a first stair step structure extending in the first direction, and each of the stack structures comprising a plurality of electrodes vertically stacked to comprise a second stair step structure extending in the second direction,
• wherein the first and second stair step structures of the first electrode structure are on the first connection region, and
• wherein the first and second stair step structures of the second electrode structure are on the second connection region.