NONVOLATILE SEMICONDUCTOR MEMORY DEVICE HAVING REDUCED ELECTRICAL STRESS
First Claim
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1. A nonvolatile semiconductor memory comprising:
- a floating formation switch coupled to a bit line in a memory cell array, the floating formation switch maintaining a channel voltage of memory cells coupled to the bit line at a level above a power supply voltage when the bit line comprises a non-selected bit line, reducing electrical stress applied to the memory cells during a read operation.
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Abstract
A nonvolatile semiconductor memory includes a floating formation switch coupled to a bit line in a memory cell array. The floating formation switch maintains a channel voltage of memory cells coupled to the bit line at a level above a power supply voltage when the bit line is a non-selected bit line, which reduces electrical stress applied to the memory cells connected to the non-selected bit line during a read operation.
73 Citations
20 Claims
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1. A nonvolatile semiconductor memory comprising:
a floating formation switch coupled to a bit line in a memory cell array, the floating formation switch maintaining a channel voltage of memory cells coupled to the bit line at a level above a power supply voltage when the bit line comprises a non-selected bit line, reducing electrical stress applied to the memory cells during a read operation. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A nonvolatile semiconductor memory having a memory cell array comprising a plurality of cell strings, each cell string comprising a string selection transistor having a drain connected to a bit line, a ground selection transistor having a source connected to a common source line, and a plurality of memory cell transistors having channels connected in series between a source of the string selection transistor and a drain of the ground selection transistor, the nonvolatile semiconductor memory comprising:
a plurality of floating formation switches corresponding to the plurality of cell strings, each floating formation switch maintaining a channel voltage of each of the plurality of memory cell transistors coupled to a corresponding bit line at a level higher than a power supply voltage when a cell string corresponding to the bit line is not selected, reducing electrical stress on the memory cell transistors of the corresponding cell string when another cell string of the plurality of cell strings in the memory cell array is selected in a read operating mode. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18)
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19. A nonvolatile semiconductor memory device, comprising:
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a memory cell array comprising a plurality of cell strings, each cell string comprising a first selection transistor having a drain connected to a corresponding bit line, a second selection transistor having a source coupled to a common source line, a plurality of memory cell transistors having channels connected in series to a source of the first selection transistor and which each have a floating gate, and third and fourth selection transistors having channels connected in series to each other between a source of a last memory cell transistor of the plurality of memory cell transistors and a drain of the second selection transistor, the third and fourth selection transistors having different threshold voltage values; and a read operation controller for controlling one of the third and fourth selection transistors of one of the plurality of cell strings to be turned OFF and a channel voltage of the memory cell transistors of the cell string to be increased to be self-boosted to a level above a power supply voltage when a bit-line corresponding to the cell string is not selected, reducing electrical stress applied to the memory cell transistors belonging to the cell string, when another one of the plurality of cell strings is selected in a read operating mode. - View Dependent Claims (20)
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Specification