Nonvolatile semiconductor memory device and memory system

A memory system comprising:

• a nonvolatile semiconductor memory comprising a memory cell array and word lines, the memory cell array comprising blocks that each comprise electrically rewritable memory cells, each of the blocks comprising NAND strings that each comprise a preset number of memory cells serially connected in a first direction, the word lines being respectively connected to memory cell groups arranged in a second direction that intersects with the first direction in the block;
• and
• a host 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.

A memory system comprising:

• a nonvolatile semiconductor memory comprising a memory cell array and word lines, the memory cell array comprising blocks that each comprise electrically rewritable memory cells, each of the blocks comprising NAND strings that each comprise a preset number of memory cells serially connected in a first direction, the word lines being respectively connected to memory cell groups arranged in a second direction that intersects with the first direction in the block;
• and
• a host 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 perform a process (B) of moving data of the fail block to another block.