A memory device includes a memory cell array, a row decoder connected to the memory cell array by a plurality of string selection lines, a plurality of word lines, and a plurality of ground selection lines, and a common source line driver connected to the memory cell array by a common source line. The memory cell array is located in an upper chip, at least a portion of the row decoder is located in a lower chip, at least a portion of the common source line driver is located in the upper chip, and a plurality of upper bonding pads of the upper chip are connected to a plurality of lower bonding pads of the lower chip to connect the upper chip to the lower chip.