A composite semiconductor memory device, comprising: a plurality of nonvolatile memory devices; and an interface device connected to the plurality of nonvolatile memory devices and for connection to a memory controller, the interface device comprising an error correction coding (ECC) engine. Also, a memory system, comprising: a memory controller; and at least one composite semiconductor memory device configured for being written to and read from by the memory controller and comprising a built-in error correction coding (ECC) engine. Also, a memory system, comprising: a composite semiconductor memory device comprising a plurality of nonvolatile memory devices; and a memory controller connected to the at least one composite semiconductor memory device, for issuing read and write commands to the composite semiconductor memory device to cause data to be written to or read from individual ones of the nonvolatile memory devices; the composite semiconductor memory device providing error-free writing and reading of the data.