A memory device includes a first semiconductor chip including a memory cell array disposed on a first substrate, and a first bonding metal on a first uppermost metal layer of the first semiconductor chip, and a second semiconductor chip including circuit devices disposed on a second substrate and a second bonding metal on a second uppermost metal layer of the second semiconductor chip, the circuit devices providing a peripheral circuit operating the memory cell array. The first and second semiconductor chips are electrically connected to each other by the first bonding metal and the second bonding metal in a bonding area. A routing wire electrically connected to the peripheral circuit is disposed in one or both of the first and second uppermost metal layers and is disposed in a non-bonding area in which the first and second semiconductor chips are not electrically connected to each other.