A memory cell array includes memory cells that are formed in vertical channels extended in a vertical direction with respect to a substrate. The vertical channels are arranged in a zigzag manner in parallel to the first direction. A read-write circuit is connected to the memory cells via bit lines. An address decoder decodes an address to provide decoded address signals to the read-write, circuit. The memory cells include outer cells and inner cells. A distance between one of the outer cells and a common source node is smaller than a distance between one of the inner cells and the common source node. Data of the memory cells are distributed among ECC sectors and a data input-output order of the memory cells is arranged such that each ECC sector has substantially the same number of the outer cells and the inner cells. Each ECC sector corresponds to an ECC operation unit.