CPC G11C 16/26 (2013.01) [G11C 11/5628 (2013.01); G11C 16/0483 (2013.01); G11C 16/08 (2013.01); G11C 16/10 (2013.01); G11C 16/14 (2013.01); G11C 16/3427 (2013.01); G11C 16/349 (2013.01)] | 20 Claims |
1. A nonvolatile semiconductor memory device comprising:
a memory cell array which comprises: a memory string having a plurality of memory cells connected in series therein; a first select transistor connected to one end of the memory string; a second select transistor connected to the other end of the memory string; a bit line connected to the memory string via the first select transistor; a source line connected to the memory string via the second select transistor; and a word line connected to a control gate electrode of each of the memory cells; and
a control circuit configured to apply a reading voltage to the control gate electrode of a selected memory cell in the memory string to determine whether the selected memory cell is conductive or not while applying to the control gate electrode of a non-selected memory cell in the memory string a reading pass voltage for rendering the non-selected memory cell conductive regardless of data stored in the non-selected memory cell, and thereby performing a reading operation for the selected memory cell,
the control circuit being configured to
in a first stage of the reading operation, apply a first reading voltage to a selected word line connected to the control gate electrode of the selected memory cell and apply a first reading pass voltage to a first non-selected word line connected to the control gate electrode of a first non-selected memory cell, and
in a second stage subsequent to the first stage of the reading operation, apply a second reading voltage to the selected word line and apply to the first non-selected word line a second reading pass voltage of which voltage value is different from that of the first reading pass voltage.
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