Semiconductor memory device and method for writing therein

摘要

According to one embodiment, a semiconductor memory device includes a plurality of blocks in a memory cell, each of the blocks acting as an erasure unit of data, the block including a plurality of pages, each of the pages including a plurality of memory cell transistors, each of the memory cell transistors being configured to be an erasure state or a first retention state based on a threshold voltage of the memory cell transistor, and a controller searching data in the block with respect to, writing a first flag denoting effective into a prescribed page of the block with the erasure state, and writing the first flag denoting non-effective into a prescribed page of the block with the first retention state, reading out the prescribed page of the block with the first retention state, and determining that the block is writable when the first flag denotes effective.

主权项

1. A semiconductor memory device comprising:
a plurality of blocks in a memory cell, each of the blocks acting as an erasure unit of data, and including a plurality of pages, each of the pages including a plurality of memory cell transistors, each of the memory cell transistors being configured to be in an erasure state or in a first retention state based on a threshold voltage thereof; and a controller configured to search in each said block with respect to data, to write a first flag to denote effective into a prescribed page of the block with the prescribed page in the erasure state, to write the first flag to denote non-effective into the prescribed page of the block with the prescribed page in the first retention state, to read out the prescribed page of the block with the prescribed page in the first retention state, and to determine that the block is writable when the first flag denotes effective.