Sandisk Technologies Inc.

Motoo Ohaga

Naohiro Hosoda

Hiroyuki Ogawa

Shinsuke Yada

As block sizes in NAND memory continue to increase in size and density, in can be useful to access less than all of the block, such as sub-block or subset of the blocks NAND strings, in order to reduce read disturbs, reduce power consumption, and increase operating speeds. Although this sort of separation of sub-block can be achieved by independently biasable select gates, the sort of select gate structure can face processing difficulties, particularly at the source side of three dimensional NAND structures. To avoid these difficulties while still providing individually selectable sub-blocks, the following introduces word line based selectors, where multiple word lines of a blocks are programmed with different sets of threshold voltages, allowing them to be biased for individual access of sub-blocks.

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Nagoya, Japan

Motoo Ohaga