A three-dimensional stacked memory device includes a buffer die having a plurality of core die memories stacked thereon. The buffer die is configured as a buffer to occupy a first space in the buffer die. The first memory module, disposed in a second space unoccupied by the buffer, is configured to operate as a cache of the core die memories. The controller is configured to detect a fault in a memory area corresponding to a cache line in the core die memories based on a result of a comparison between data stored in the cache line and data stored in the memory area corresponding to the cache line in the core die memories. The second memory module, disposed in a third space unoccupied by the buffer and the first memory module, is configured to replace the memory area when the fault is detected in the memory area.