US Patent 7602638 Semiconductor memory device

A semiconductor memory device is provided which can achieve high performance, such as an improvement in reliability, an improvement in yield, and the like, without increasing the chip area. The semiconductor memory device is a non-volatile semiconductor memory device operable to program and erase data, and hold the data in the absence of a supplied voltage, comprising a memory cell including a first charge localized portion and a second charge localized portion each operable to store static charge corresponding to the data. The second charge localized portion stores static charge corresponding to static charge which should be stored in the first charge localized portion, thereby serving as a backup to the first charge localized portion.