Semiconductor memory device and method of operation the same

A semiconductor memory device includes a first plane and a second plane each configured to include a plurality of memory cells, and a data transfer circuit configured to transfer first data, stored in the memory cells of the first plane, to the second plane and transfer second data, stored in the memory cells of the second plane, to the first plane when a copyback operation is performed and to transfer the first data or the second data to an I/O circuit when a read operation is performed.