A semiconductor memory device is provided. The semiconductor memory device includes an error correction code block and a memory. The error correction code block performs error correction encoding for user data to generate parity data. The memory stores the user data and the parity data. The error correction code block generates parity data, including a number of bits equal to at least 2t, wherein t is a natural number, and the bits of the parity data distinguish free page data from user data that is equal to the free page data.