US Patent 7272058 Nonvolatile semiconductor memory device having redundant relief technique

A nonvolatile semiconductor memory device including associating means for associating a faulty block with a redundant block, a block switching circuit for selecting the associated redundant block when a memory block is associated with the redundant block, an error detection circuit for detecting an error in an accessing operation to the memory block, a faulty block identification circuit for identifying the memory block having the detected error as a faulty block when the error is detected and associating the faulty block with the redundant block in the case where the redundant block which is not associated with the faulty block exists.