Multiple select gates with non-volatile memory cells
Multiple select gates in association with non-volatile memory cells are described. Various embodiments include multiple select gate structure, process, and operation and their applicability for memory devices, modules, and systems. In one embodiment a memory array is described. The memory array includes a number of select gates coupled in series to a number of non-volatile memory cells. A first select gate includes a control gate and a floating gate electrically connected together and a second select gate includes a control gate and a floating gate which are electrically separated by a dielectric layer.
1. A memory array, comprising:
a number of non-volatile memory cells;
a number of select gates coupled in series to the number of non-volatile memory cells;
wherein a first select gate includes a control gate and a floating gate electrically connected together by a conductive strap through a dielectric layer; and
wherein a second select gate includes a control gate and a floating gate which are electrically coupled but separated by a dielectric layer.
2. The array of claim 1 , wherein the second select gate is adjacent the number of non-volatile memory cells.
3. The array of claim 1 , wherein the second select gate has a threshold voltage which is substantially the same as a threshold voltage for each of the number of non-volatile memory cells.
4. The array of claim 1 , wherein the number of non-volatile memory cells includes a number of non-volatile memory cells coupled in series.
5. The array of claim 1 , wherein the number of non-volatile memory cells includes a NAND string.
6. A memory array, comprising:
a NAND string of non-volatile memory cells;
a number of source select gates on a source side of the string;
a drain select gate on a drain side of the string; and
wherein the number of source select gates includes at least one source select gate having a control gate and a floating gate electrically connected together by a conductive strap through a dielectric layer, and includes at least one source select gate having a control gate and a floating gate which are electrically separated by a dielectric layer.
7. The array of claim 6 , wherein at least one of the number of source select gates has a pitch that is substantially equal to a pitch of each non-volatile memory cell in the NAND string.
8. The array of claim 6 , wherein the array includes a pair of series coupled source select gates on the source side of the NAND string, and a pair of series coupled drain select gates on the drain side of the NAND string.
9. The array of claim 6 , wherein the at least one source select gate having the control gate and the floating gate which are electrically separated by the dielectric layer has a cell structure which is substantially the same as a cell structure for each non-volatile memory cell in the NAND string.
10. The array of claim 6 , wherein the at least one source select gate having the control gate and the floating gate which are electrically separated by the dielectric layer has a threshold voltage which is substantially the same as a threshold voltage for each non-volatile memory cell in the NAND string.
11. A memory array, comprising:
a string of non-volatile memory cells;
a number of source select gates on a source side of the string and coupled in series with the string;
a number of drain select gates on a drain side of the string and coupled in series with the string; and
wherein at least one select gate on a cell side of the string has a control gate and a floating gate electrically separated by a dielectric layer from one another and is coupled in series with at least one select gate having a control gate and a floating gate which are electrically connected by a conductive strap through a dielectric layer.
12. The memory array of claim 11 , wherein a threshold voltage of the at least one select gate on the cell side of the string is substantially the same as a threshold voltage for each non-volatile memory cell of the string.
13. The memory array of claim 11 , wherein the string of-non-volatile memory cells is a NAND string.
14. The memory array of claim 11 , wherein the at least one select gate on the cell side is substantially the same size as each non-volatile memory cell of the string.
15. A memory device, comprising:
an array of non-volatile memory cells including a string of non-volatile memory cells;
circuitry for control and access to the array of non-volatile memory cells;
wherein the array of non-volatile memory cells includes:
a first number of select gates coupled to a source side of the string of non-volatile memory cells, wherein a first one of the first number of select gates is coupled to a source line and has a control gate and a floating gate electrically connected together by a conductive strap through a dielectric layer, and wherein a second one of the first number of select gates is coupled to a first one of the string of non-volatile memory cells and has a control gate and a floating gate electrically separated by a dielectric layer from one another; and
a second number of select gates coupled to a drain side of the string of non-volatile memory cells, and wherein a last one of the second number of select gates is coupled to a bit line.
16. The memory device of claim 15 , wherein:
the second number of select gates includes a pair of select gates series coupled to the drain side of the string, and coupled to a single drain select line;
the first one of the first number of select gates is coupled to a first source select line; and
the second one of the first number of select gates is coupled to a second source select line.
17. The memory device of claim 15 , wherein the second one of the first number of select gates has a gate length which is substantially equivalent to a gate length of each non-volatile memory cell in the string.
18. A memory module, comprising:
a number of contacts;
two or more memory devices, each having access lines selectively coupled to the number of contacts; and
wherein at least one of the memory devices includes:
an array of non-volatile memory cells including a string of non-volatile memory cells;
circuitry for control and access to the array of non-volatile memory cells;
wherein the array of non-volatile memory cells includes:
a pair of source select gates series coupled to the string, wherein a first one of the source select gates has a control gate and a floating gate electrically connected together by a conductive strap through a dielectric layer, and wherein a second one of the source select gates has a control gate and a floating gate which are separated by a dielectric; and
a pair of drain select gates series coupled to the string.
19. An electronic system, comprising:
a processor, and
a memory device coupled to the processor, wherein the memory device includes:
an array of non-volatile memory cells including a NAND string;
circuitry for control and access to the array of non-volatile memory cells; and
wherein the ray of non-volatile memory cells includes:
a first and a second source select gate series connected to the NAND string, wherein:
the first source select gate has a control gate and a floating gate which are electrically connected by a conductive strap through a dielectric layer; and
the second source select gate has a control gate and a floating gate separated by a dielectric, and has a threshold voltage and a cell size which are substantially equal to a threshold voltage and a cell size of each non-volatile memory cell in the NAND string; and
a drain select gate connected to the NAND string, the drain select gate has a control gate and a floating gate which are electrically connected by a conductive strap through a dielectric layer.
20. The electronic system of claim 19 , wherein a threshold voltage of the first source select gate is different from the threshold voltage of the second source select gate.
21. The electronic system of claim 19 , wherein the system includes a first and a second drain select gate series connected to the NAND string, wherein:
the first drain select gate has a control gate and a floating gate which are electrically connected by a conductive strap through a dielectric layer; and
the second drain select gate has a control gate and a floating gate separated by a dielectric, and has a threshold voltage and a cell size which are substantially equal to a threshold voltage and a cell size of each non-volatile memory cell in the NAND string.