Non-volatile semiconductor memory device
View Patent ↗In one embodiment, a control circuit executes a first page writing operation, a first verify operations, a second page writing operation, a second verify operations, a step-up operation. The control circuit executes the first page writing operation which forms an intermediate distribution, and a first read operation which reads data form the intermediate distribution by using a determine voltage higher than a first verify voltage with a first value, and changes a second verify voltage based on the result of the first read operation.
1. A non-volatile semiconductor memory device comprising:
a memory cell array including a plurality of memory strings, each memory string including a plurality of memory cells connected in series, each memory cell storing multi-valued data;
a word line that connects to one of the a plurality memory cells;
a bit line that is connected to a first end of the memory string;
a source line connected to a second end of the memory string;
a sense amplifier circuit configured to determine the data to be stored in the memory cell by detecting the potential or the electric current of the bit lines; and
a control circuit configured to execute a first page writing operation to form an intermediate voltage distribution by changing a threshold voltage of the memory cells connected to the word line,
a first verify operation to determine if the first page writing operation to the memory cell has been completed by using a first verify voltage,
a second page writing operation to change the intermediate voltage distribution,
a second verify operation to determine if the second page writing operation to the memory cell has been completed by using a second verify voltage and a step-up operation that increases the program voltage by a step-up voltage amount based on results of the verify reading,
wherein the control circuit is configured to execute the first page writing operation which forms the intermediate voltage distribution, and a first read operation which reads data from the intermediate voltage distribution by using a determine voltage higher than the first verify voltage, and to change the second verify voltage based only on the result of the first read operation.
2. The non-volatile semiconductor memory device according to claim 1 , wherein the control circuit is configured to change the value of the step-up voltage used in the second page write operation based only on the result of the first read operation.
3. The device of claim 1 , further comprising:
a bit scan circuit wherein the bit scan circuit counts the number of the memory cells which exceed the determine voltage.
4. The device of claim 3 wherein the second verify voltage is changed by the number of the memory cells which exceed the determine voltage in the first read operation.
5. The device of claim 2 , further comprising:
a bit scan circuit wherein the bit scan circuit counts the number of the memory cells which exceed the determine voltage, and the step-up voltage is changed by the number of the memory cells which exceed the determine voltage in the first read operation.
6. The device of claim 4 wherein a change value of the second verify voltage is larger, so that the number of the memory cells counted by the bit scan circuit is large.
7. The device of claim 5 wherein a change value of the step-up voltage is smaller, so that the number of the memory cells counted by the bit scan circuit is large.
8. The device of claim 6 wherein a polarity of threshold distributions is formed in the second page writing operation, and the larger a value of the threshold distributions, the larger the change value of the second verify voltage.
9. The device of claim 1 , further comprising:
a sense amplifier circuit connected to the bit line,
the sense amplifier circuit for detecting electrical potential or current to the bit line.