NONVOLATILE SEMICONDUCTOR STORAGE DEVICE AND OPERATION METHOD THEREOF

摘要

A multi-valued nonvolatile semiconductor storage device and an operation method thereof capable of setting a plurality of positive levels having positive threshold voltages and a plurality of negative levels having negative threshold voltages for storing information in a charge storage layer is provided. According to one aspect, there is provided a nonvolatile semiconductor storage device which comprises a storage element provided on a first surface of a semiconductor layer and including a charge storage layer provided with a plurality of positive levels having positive threshold voltages and a plurality of negative levels having negative threshold voltages to store information, and a back electrode provided on a second surface of the semiconductor layer to be opposite to the storage element, the back electrode being configured to apply a voltage which converts information stored in the negative level of the charge storage layer to information having a positive threshold voltage.