A semiconductor memory system or device includes a memory cell array and an address converter. The memory cell array includes a plurality of memory blocks, and there is at least one block that serves as a buffer. Each of the memory blocks includes at least one memory cell row. An address converting circuit along with a block copy circuit performs a block copy operation of copying data of a first memory block, which is a source block among the memory blocks, into a second block, which is a buffer or destination block, and maps a first logical address for accessing the first memory block onto a physical address designating the second block. The first memory block then can serve as a new destination block after the block copy operation of the first memory block is completed.