High-speed writable semiconductor memory device
A memory cell array has a plurality of series connected memory cells connected to word lines and bit lines and arranged in a matrix. A select transistor selects from the word lines. A control circuit controls potentials of the word lines and bit lines in accordance with input data, and controls a data write operation, a data read operation, and a data erase operation executed on the memory cells. The select transistor is formed on a substrate. For a read operation, the substrate is supplied with a first negative voltage, a selected word line is supplied with a first voltage (first voltage≧first negative voltage), and unselected word lines are supplied with a second voltage.
1. A semiconductor memory device comprising:
a memory cell array having word lines and bit lines and in which a plurality of series connected memory cells are arranged in a matrix, one of a plurality of threshold voltages being set for each of the memory cells;
a select transistor which selects from the word lines; and
a control circuit which controls potentials of the word lines and bit lines in accordance with input data, the control circuit controlling a data write operation, a data read operation, and a data erase operation executed on the memory cells,
wherein the select transistor is formed on a substrate, and for a read operation, the substrate is supplied with a first negative voltage, a selected word line is supplied with a first voltage (first voltage≧first negative voltage), and unselected word lines are supplied with a second voltage.
2. The device according to claim 1 , wherein a part of the control circuit is formed in an N-type well region formed in the substrate of a P type and in a P-type well region formed in the N-type well region.
3. The device according to claim 1 , wherein the control circuit comprises:
a pump circuit which generates a negative voltage in response to a clock signal;
a detection circuit connected to an output end of the pump circuit, the detection circuit detecting an output voltage from the pump circuit;
an oscillator which generates the clock signal; and
a control section to which an output signal from the detection circuit is supplied, the control section controlling the oscillator in accordance with the output signal from the detection circuit.
4. The device according to claim 1 , wherein each of the memory cells stores one of a plurality of threshold voltages, and some of the plurality of threshold voltages are negative.
5. The device according to claim 1 , wherein a central part of the plurality of threshold voltages is 0 V.
6. The device according to claim 1 , wherein a central part of the plurality of threshold voltages is a threshold voltage with a minimum data retention.
7. A semiconductor memory device comprising:
a memory cell array having word lines and bit lines and in which a plurality of series connected memory cells are arranged in a matrix, one of a plurality of threshold voltages being set for each of the memory cells;
a select transistor which selects from the word lines; and
a control circuit which controls potentials of the word lines and bit lines in accordance with input data to control a data write operation, a data read operation, and a data erase operation executed on the memory cells,
wherein the select transistor is formed on a substrate, and for a write operation, the substrate is supplied with a second negative voltage, and a part of unselected word lines are supplied with a third voltage (third voltage≧second negative voltage).
8. The device according to claim 7 , wherein the control circuit supplies the third voltage to unselected word lines located at least closer to a source line than a write target memory cell.
9. The device according to claim 7 , wherein a part of the control circuit is formed in an N-type well region formed in the substrate of a P type and in a P-type well region formed in the N-type well region.
10. The device according to claim 7 , wherein each of the memory cells stores one of a plurality of threshold voltages, and some of the plurality of threshold voltages are negative.
11. A semiconductor memory device comprising:
a memory cell array in which a plurality of series connected memory cells connected to word lines and bit lines and for each of which one of a plurality of threshold voltages is set are arranged in a matrix;
a select transistor which selects from the word lines; and
a control circuit which controls potentials of the word lines and bit lines in accordance with input data to control a data write operation, a data read operation, and a data erase operation executed on the memory cells,
wherein the select transistor is formed on a substrate, and for an erase verify read operation, the substrate is supplied with a third negative voltage, and a selected word line is supplied with a fourth voltage (fourth voltage≧third negative voltage).
12. The device according to claim 11 , wherein a part of the control circuit is formed in an N-type well region formed in the substrate of a P type and in a P-type well region formed in the N-type well region.
13. The device according to claim 11 , wherein each of the memory cells stores one of a plurality of threshold voltages, and some of the plurality of threshold voltages are negative.
14. A semiconductor memory device comprising:
a memory cell array in which a plurality of series connected memory cells connected to word lines and bit lines are arranged in a matrix;
a control section which supplies a first voltage to a first bit line of the bit lines corresponding to a first memory cell to which a first threshold voltage is written, the control section supplying a second bit line corresponding to a second memory cell to which a second threshold voltage lower than the first threshold voltage is written, with a voltage obtained by adding the first voltage to a difference voltage between the first threshold voltage and the second threshold voltage, the control section supplying a third bit line connected as the source line and corresponding to the first memory cell, with a second voltage lower than the first voltage, the control section supplying a fourth bit line connected as the source line and corresponding to the second memory cell, with a voltage obtained by adding the second voltage to the difference voltage between the first threshold voltage and the second threshold voltage;
a first data storage circuit which detects and holds the potential of the first bit line during a write data verify operation; and
a second data storage circuit which detects and holds the potential of the second bit line during the write data verify operation.
15. The device according to claim 14 , wherein the control section supplies a selected word line with the first threshold voltage.
16. The device according to claim 14 , wherein the second voltage is a ground potential.
17. The device according to claim 14 , further comprising:
a first selection circuit which connects one of the two adjacent bit lines to one end of the plurality of series connected memory cells in accordance with a first selection signal; and
a second selection circuit which connects the other of the two adjacent bit lines to the other end of the plurality of series connected memory cells as a source line, in accordance with a second selection signal.
18. The device according to claim 14 , wherein each of the memory cells stores one of a plurality of threshold voltages, and some of the plurality of threshold voltages are negative.
19. The device according to claim 14 , wherein an unselected one of the plurality of bit lines functions as a source line.
20. The device according to claim 14 , further comprising:
an NAND cell including the memory cell;
a first contact connecting a first bit line with one end of the NAND cell; and
a second contact connecting a second bit line with another end of the NAND cell;
wherein the first and second contacts are spaced and arranged in longitudinal direction of the first and second bit lines.