Semiconductor memory device capable of shortening erase time
First Claim
1. A semiconductor memory device comprising:
- a memory cell array in which a plurality of memory cells are arranged in a matrix;
a plurality of word lines connected to the plurality of memory cells;
a plurality of bit lines connected to each of one end of the memory cells; and
a control circuit configured to control the potentials of said plurality of word lines and said plurality of bit lines,wherein the control circuit sets a first voltage to first word lines of k (k is a natural number) of the plurality of word lines in an erase verify operation, sets a second voltage to second word lines of h (h is a natural number) of the plurality of word lines, and carries out the erase verify operation,wherein the memory cells constitute a plurality of blocks as an erase unit, andwherein the memory cells in the blocks are series-connected and which constitutes a series circuit, the second word lines are connected to the memory cells arranged at both ends of the series circuit, and the first word lines are connected to the another memory cells of the series circuit.
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Accused Products
Abstract
In a memory cell array, a plurality of memory cells connected to a plurality of word lines and a plurality of bit lines are arranged in a matrix. A control circuit controls the potentials of said plurality of word lines and said plurality of bit lines. In an erase operation, the control circuit erases an n number of memory cells (n is a natural number equal to or larger than 2) of said plurality of memory cells at the same time using a first erase voltage, carries out a verify operation using a first verify level, finds the number of cells k (k≦n) exceeding the first verify level, determines a second erase voltage according to the number k, and carries out an erase operation again using the second erase voltage.
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Citations
16 Claims
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1. A semiconductor memory device comprising:
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a memory cell array in which a plurality of memory cells are arranged in a matrix; a plurality of word lines connected to the plurality of memory cells; a plurality of bit lines connected to each of one end of the memory cells; and a control circuit configured to control the potentials of said plurality of word lines and said plurality of bit lines, wherein the control circuit sets a first voltage to first word lines of k (k is a natural number) of the plurality of word lines in an erase verify operation, sets a second voltage to second word lines of h (h is a natural number) of the plurality of word lines, and carries out the erase verify operation, wherein the memory cells constitute a plurality of blocks as an erase unit, and wherein the memory cells in the blocks are series-connected and which constitutes a series circuit, the second word lines are connected to the memory cells arranged at both ends of the series circuit, and the first word lines are connected to the another memory cells of the series circuit. - View Dependent Claims (2, 3, 4, 5, 6, 16)
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7. A semiconductor memory device comprising:
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a memory cell array in which a plurality of memory cells are arranged in a matrix; a plurality of word lines connected to the plurality of memory cells; a plurality of bit lines connected to each of one end of the memory cells; and a control circuit configured to control the potentials of said plurality of word lines and said plurality of bit lines, wherein the control circuit sets a first voltage to first word lines of k (k is a natural number) of the plurality of word lines in an erase operation, sets a second voltage (the first voltage <
the second voltage) to second word lines of h (h is a natural number) of the plurality of word lines, sets a third voltage (the third voltage <
the first voltage) to a third word lines of n (n is a natural number) of the plurality of word lines, and carries out the erase operation. - View Dependent Claims (8, 9, 10, 11, 12, 13)
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14. A semiconductor memory device comprising:
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a memory cell array in which a plurality of memory cells are arranged in a matrix; a plurality of word lines connected to the plurality of memory cells; a plurality of bit lines connected to each of one end of the memory cells; and a control circuit configured to control the potentials of said plurality of word lines and said plurality of bit lines, wherein the control circuit sets a first voltage to first word lines of k (k is a natural number) of the plurality of word lines in an erase operation, sets a second voltage (the first voltage <
the second voltage) to a second word lines of h (h is a natural number) of the plurality of word lines, and carries out the erase operation,wherein the memory cells constitute a plurality of blocks as an erase unit, and wherein the memory cells in the blocks are series-connected and which constitutes a series circuit, the second word lines are connected to the memory cells arranged at both ends of the series circuit, and the first word lines are connected to another memory cells of the series circuit. - View Dependent Claims (15)
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Specification