Patent ID: 6385085
Filing Date: 2002-05-07
Classification: G11C

Abstract:
A nonvolatile memory system comprising:a novolatile memory including a pluarlity of memory cells each of which has one of pluarlity of threshold voltage distributions; and a controller controlling an operation to said nonvolatile memory, wherein said operation includes a read data operation, a write data operation and an erase data operation, wherein said nonvolatile memory reads out data from ones of memory cells, when said controller controls said read data operation, wherein said read data operation, ones of said memory cells are supplied intially with a first read voltage having a voltage potential between a first lowest threshold voltage disrtubution and a second lowest thresold voltage distribution, and wherein said ones of said memory cells without stored first data corresponding to said lowest thresold voltage distribution are supplied a second read voltage having a voltage potential between a second lowest threshold voltage and a third lowest threshold voltage next.