NONVOLATILE STORAGE DEVICE

摘要

PROBLEM TO BE SOLVED: To improve performance of a read/write speed and retention error resistance in a nonvolatile storage device mounting a nonvolatile memory and a controller.

SOLUTION: A nonvolatile memory 3 can store information more than 2 bits and enables the first read-out for outputting information read out from the nonvolatile memory cell as 1 bit information and second read-out for outputting the information read out as 2 bit information. A controller 2 performs the first read-out when reading the first information from the nonvolatile memory and performs the second read-out when reading the second information. The first read-out can raise a read-out speed with compared to the second read-out. In writing into the first reading object area, the retention error resistance of the first information is improved with a threshold voltage as one of the voltages selected between a voltage of upper limit threshold voltage distribution and a voltage of lower limit threshold voltage distribution.

COPYRIGHT: (C)2004,JPO