Nonvolatile memory system semiconductor memory and writing method
First Claim
1. A non-volatile memory system, comprising:
- a memory array including a plurality of memory cells in which each memory cell stores a data by threshold voltage corresponding to a first state and a second state, and a word line coupled to gates of the plurality of memory cells; and
a sequencer which controls procedures of changing the threshold voltage of the plurality of memory cells in response to corresponding commands;
wherein the plurality of memory cells includes a first group of memory cells having a threshold voltage corresponding to the first state, and a second group of memory cells having a threshold voltage corresponding to the second state;
wherein said sequencer includes an erase command procedure which puts the threshold voltage of the plurality of memory cells into the first state, and a write command procedure which puts the threshold voltage of at least a selected one of the first group of memory cells into the second state; and
wherein the write command procedure includes a first step in which the threshold voltage of the second group of memory cells is changed toward a voltage direction from the second state to the first state, and a second step in which the threshold voltage of the second group of memory cells and at least a selected one of the first group of memory cells are changed to the second state.
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Accused Products
Abstract
A nonvolatile semiconductor memory recovers variation in the threshold of a memory cell due to disturbance related to a word line. The nonvolatile memory continuously performs many writing operations without carrying out single-sector erasing after each writing operation, performing the additional writing operations quicker than the usual writing operation, and lightening the burden imposed on software for use in additional writing. The data stored in a designated sector is read out before being saved in a register, and the selected sector is subjected to single-sector erasing when a predetermined command is given. Then write expected value data is formed from the saved data and data to be additionally written, completing the writing operation.
94 Citations
31 Claims
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1. A non-volatile memory system, comprising:
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a memory array including a plurality of memory cells in which each memory cell stores a data by threshold voltage corresponding to a first state and a second state, and a word line coupled to gates of the plurality of memory cells; and a sequencer which controls procedures of changing the threshold voltage of the plurality of memory cells in response to corresponding commands; wherein the plurality of memory cells includes a first group of memory cells having a threshold voltage corresponding to the first state, and a second group of memory cells having a threshold voltage corresponding to the second state; wherein said sequencer includes an erase command procedure which puts the threshold voltage of the plurality of memory cells into the first state, and a write command procedure which puts the threshold voltage of at least a selected one of the first group of memory cells into the second state; and wherein the write command procedure includes a first step in which the threshold voltage of the second group of memory cells is changed toward a voltage direction from the second state to the first state, and a second step in which the threshold voltage of the second group of memory cells and at least a selected one of the first group of memory cells are changed to the second state. - View Dependent Claims (2, 3, 4, 18, 21, 24)
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5. A non-volatile memory system, comprising:
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a memory array including a plurality of memory cells in which each memory cell stores a data by threshold voltage corresponding to a first state and a second state; a word line coupled to gates of the plurality of memory cells; a plurality of data lines, each data line being coupled to each of the plurality of memory cells; a plurality of sense latches, each sense latch being coupled to each of the plurality of data lines; and a data input/output terminal coupled to the plurality of data lines; and a sequencer which controls procedures of changing the threshold voltage of the plurality of memory cells in response to corresponding commands; wherein the plurality of memory cells includes a first group of memory cells having a threshold voltage corresponding to the first state, and a second group of memory cells having a threshold voltage corresponding to the second state; wherein said sequencer includes an erase command procedure which puts the threshold voltage of the plurality of memory cells into the first state, and a write command procedure which puts the threshold voltage of at least a selected one of the first group of memory cells into the second state; and wherein the write command procedure includes a first step of storing a first data inputted from the input/output terminal to each of the plurality of sense latches;
a second step of reading a second data from each of the plurality of memory cells onto each of the plurality of data lines, synthesizing a third data from the first data and the second data, and storing the third data in each of the plurality of sense latches;
a third step of changing the threshold voltage of the plurality of memory cells toward a voltage direction from the second state to the first state; and
a fourth step of putting into the second state the threshold voltage of at least one of the memory cells indicated by the third data. - View Dependent Claims (6, 7, 19, 22, 25)
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8. A non-volatile memory system, comprising:
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a memory array including a plurality of memory cells in which each memory cell stores a data by threshold voltage corresponding to a first state and a second state, and a word line coupled to gates of the plurality of memory cells; and a sequencer which controls procedures of changing the threshold voltage of the plurality of memory cells in response to corresponding commands; wherein the plurality of memory cells includes a first group of memory cells having a threshold voltage corresponding to the first state, and a second group of memory cells having a threshold voltage corresponding to the second state; wherein said sequencer includes an erase command procedure which puts the threshold voltage of the plurality of memory cells into the first state by applying a first voltage to the word line, and a first write command procedure which puts the threshold voltage of at least one of the first group of memory cells into the second state by applying a second voltage to the word line; and wherein said sequencer also includes a second write command procedure which puts the threshold voltage of at least one of the first group of memory cells into the second state by applying the first voltage and the second voltage to the word line. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15, 16, 17, 20, 23, 26)
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27. A non-volatile memory formed on a single semiconductor chip, comprising:
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a plurality of memory cells, each memory cell including a transistor, storing information by threshold voltage of the transistor; and a sequencer having a terminal to which commands are supplied, and controlling a corresponding procedure to put said plurality of memory cells into an erased state or a written state in response to each of the commands; wherein said sequencer includes a command procedure which is started by one of the commands to perform an operation of putting the threshold voltage of said plurality of memory cells into a predetermined state; and another operation of putting a part of said plurality of memory cells, which are in the written state before the one of the commands is supplied, and at least a selected one of said memory cells, which is selected from said plurality of memory cells after the one of the commands is supplied, into the written state. - View Dependent Claims (28, 29, 30, 31)
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Specification