Nonvolatile semiconductor memory device and memory system

摘要

According to one embodiment, a nonvolatile semiconductor memory device includes a memory cell array includes blocks, each of the blocks includes NAND strings that each comprise memory cells serially connected in a first direction, word lines respectively connected to memory cell groups arranged in a second direction in the block, and a controller configured to perform a process (A) of verifying one of states in which all of the memory cells included in the block are turned on (pass) and at least one memory cell is turned off (fail) by use of a first read voltage applied to unselected word lines in a data read time, and to perform a process (B) of reading data from the fail block by use of a second read voltage that is higher than the first read voltage and applied to the unselected word lines.

主权项

1. A nonvolatile semiconductor memory device comprising:
a memory cell array including a plurality of blocks, each of the plurality of blocks including a plurality of memory strings and a plurality of word lines, each of the plurality of memory strings including serially connected memory cells, one end of the serially connected memory cells is coupled to a bit line through a first select transistor and another end is coupled to a source line through a second select transistor; and a controller configured to:
read data by applying a first read pass voltage to unselected word lines and applying a read voltage to a selected word line;before a read operation is performed, apply the first read pass voltage to all of the plurality of word lines to detect an overly programmed memory cell that is not turned on even though the first read pass voltage is applied to its gate; andwhen at least one overly programmed memory cell is detected, read data by applying a second read pass voltage to the unselected word lines and applying the read voltage to the selected word line, whereinthe second read pass voltage is higher than the first read pass voltage.