Nonvolatile semiconductor memory adapted to store a multi-valued data in a single memory cell
View Patent ↗A non-volatile semiconductor memory device includes an electrically data rewritable non-volatile semiconductor memory cell and a write circuit for writing data in the memory cell, the write circuit writing a data in the memory cells by supplying a write voltage Vpgm and a write control voltage VBL to the memory cell, continuing the writing of the data in the memory cell by changing the value of the write control voltage VBL in response to an advent of a first write state of the memory cell and inhibiting any operation of writing a data to the memory cell by further changing the value of the write control voltage VBL to Vdd in response to an advent of a second write state of the memory cell.
1. A non-volatile semiconductor memory device comprising:
a non-volatile memory cell; and
a write circuit, configured to write data in the memory cell, for supplying a write voltage and a write control voltage, thereby causing an alteration in a write state of the memory cell, for changing the supply of the write control voltage in order to slow down the alteration, and for terminating the alteration amid slowing down the alteration,
wherein the write control voltage is applied to a drain electrode of the memory cell.
2. The device according to claim 1 , wherein the write voltage is stepwise increased.
3. The device according to claim 1 , wherein the write circuit determines if the write state has reached a first level, and changes the supply of the write control voltage in response to an advent of the first level.
4. The device according to claim 3 , wherein the write circuit determines if the write state has reached a second level, and terminates the alteration in response to an advent of the second level.
5. The device according to claim 1 , further comprising a word line connected to the memory cell at its gate electrode to which the write voltage is applied, and a bit line coupled to the memory cell at is drain electrode to which the write control voltage is applied.
6. The device according to claim 1 , wherein the write circuit is capable of writing data more than one bit in the memory cell.
7. A non-volatile semiconductor memory device comprising:
a non-volatile memory cell; and
a write circuit, configured to write data in the memory cell, for supplying a read voltage to the memory cell in order to read out data stored in the memory cell, for supplying a first verify voltage to the memory cell in order to determine if a write of the memory cell has reached a first level, for supplying a write voltage and a write control voltage having a first effective voltage level to the memory cell, if the write state has not reached the first level, for applying the write voltage and the write control voltage having a second effective voltage level to said memory cell, if the write state has reached the first level, for supplying a second verify voltage to the memory cell in order to determine if the write state of said memory cell has reached a second level, and for supplying the write voltage and the write control voltage having a third effective voltage level to the memory cell in order to terminate a writing data in the memory cell, if the write state has reached the second level,
wherein a difference between the read voltage and the second verify voltage is larger than a difference between the first verify voltage and the second verify voltage,
and the write control voltage is applied to a drain electrode of the memory cell.
8. The device according to claim 7 , wherein the write voltage is stepwise increased.
9. The device according to claim 7 , further comprising a word line connected to the memory cell at its gate electrode to which the write voltage is applied, and a bit line coupled to the memory cell at its drain electrode to which the write control voltage is applied.
10. The device according to claim 7 , wherein the write circuit is capable of writing data more than one bit in the memory cell.