Semiconductor memory device and data erasing method
A semiconductor memory device includes a memory cell array including a plurality of groups of memory cells above a substrate, the groups including a first group and a second group, each of the first and second groups including a first memory string and a second memory string, the first memory string including first memory cells that are disposed in a first layer, the second memory string including second memory cell that are disposed in a second layer above the first layer, and a controller configured to perform an erasing operation on the memory cells, the erasing operation including a verifying operation on the memory cells to determine on a layer by layer basis whether the memory cells failed to erase data stored therein.
1. A semiconductor memory device comprising:
a memory cell array including a first memory string and a second memory string, the first memory string including memory cells that are disposed in a first layer, the second memory string including memory cells that are disposed in a second layer above the first layer; and
a controller configured to perform an erasing operation on the memory cells, the erasing operation including a first period during which an erasing pulse is applied to the memory cells of the second memory string, and the erasing pulse is not applied to the memory cells of the first memory string, and a second period directly after the first period during which the erasing pulse is applied to both the memory cells of the first memory string and the memory cells of the second memory string.
2. The device according to claim 1 , further comprising:
a first bit line electrically connected to a first end of the first memory string;
a first source line electrically connected to a second end of the first memory string;
a second bit line electrically connected to a first end of the second memory string; and
a second source line electrically connected to a second end of the second memory string, wherein
the erasing pulse is applied to memory cells of the first memory string through at least one of the first bit line and the first source line, and to memory cells of the second memory string through at least one of the second bit line and the second source line.
3. The device according to claim 2 , wherein the erasing pulse is applied to the memory cells of the first memory string through the first bit line and to the memory cells of the second memory string through the second bit line.
4. The device according to claim 3 , wherein
the memory cell array further includes:
a third memory string including memory cells in the first layer, the third memory string being directly below the second memory string, and
a fourth memory string including memory cells in the second layer, the fourth memory string being directly above the first memory string.
5. The device according to claim 4 , wherein
the first bit line is electrically connected to a first end of the third memory string and the second source line is electrically connected to a second end of the third memory string, and
the second bit line is electrically connected to a first end of the fourth memory string and the first source line is electrically connected to a second end of the fourth memory string.
6. The device according to claim 3 , wherein the first and second source lines are maintained at a constant voltage while the erasing pulse is applied to the memory cells of the second memory string and memory cells of the first memory string.
7. The device according to claim 6 , wherein the erasing pulse is applied to the memory cells of the first memory string through the first source line and to the memory cells of the second memory string through the second source line.
8. The device according to claim 7 , wherein
the memory cell array further includes:
a third memory string including memory cells that are disposed in the first layer, the third memory string being directly below the second memory string, and
a fourth memory string including memory cells that are disposed in the second layer, the fourth memory string being directly above the first memory string.
9. The device according to claim 8 , wherein
the first bit line is electrically connected to a first end of the fourth memory string and the second source line is electrically connected to a second end of the fourth memory string, and
the second bit line is electrically connected to a first end of the third memory string and the first source line is electrically connected to a second end of the third memory string.
10. The device according to claim 7 , wherein the first and second bit lines are maintained at a constant voltage while the erasing pulse voltage is applied to the memory cells of the second memory string and the memory cells of the first memory string.