Semiconductor memory device
A semiconductor memory device according to one embodiment includes: a memory cell, the memory cell including a ferroelectric film; and a control circuit controlling the memory cell. Additionally, the control circuit determining whether the number of times of executions of a write process or an erase process on the memory cell has reached a predetermined number of times; and, if the number of times of executions has reached the predetermined number of times, executing a voltage application process in which a first voltage of a first polarity and a second voltage of a second polarity opposite to the first polarity are applied to the ferroelectric film.
1. A semiconductor memory device, comprising:
a plurality of memory cells, each of the memory cells including a ferroelectric film; and
a control circuit controlling the plurality of memory cells,
the control circuit
determining whether a bit error rate of data read from the plurality of memory cells is a predetermined rate or more; and
if the bit error rate is the predetermined rate or more, executing a voltage application process in which a first voltage of a first polarity and a second voltage of a second polarity opposite to the first polarity are applied to the ferroelectric films of the plurality of memory cells.
2. The semiconductor memory device according to claim 1 ,
the control circuit comprising:
a bit-error-rate calculating section calculating the bit error rate; and
a memory holding the calculated bit error rate, and
the control circuit
transmitting the data read from the plurality of memory cells to the bit-error-rate calculating section and acquiring the bit error rate,
holding the acquired bit error rate in the memory, and
referring to the memory at a time of determination of the bit error rate.
3. The semiconductor memory device according to claim 1 ,
the control circuit being capable of executing:
a write process in which a voltage of a first polarity is applied to the ferroelectric film; and
an erase process in which a voltage of a second polarity opposite to the first polarity is applied to the ferroelectric film,
a magnitude of the first voltage being the same as or larger than a magnitude of a maximum voltage applied to the ferroelectric film in the write process, and
a magnitude of the second voltage being the same as or larger than a magnitude of a maximum voltage applied to the ferroelectric film in the erase process.
4. The semiconductor memory device according to claim 3 ,
the control circuit
being capable of executing a write process, an erase process, a voltage application process, and an erase sequence in which data is erased from the memory cell, the erase sequence including at least one of the erase process or the voltage application process, and
if the bit error rate is the predetermined rate or more, in the erase sequence, executing the voltage application process in addition to or instead of the erase process.
5. The semiconductor memory device according to claim 3 ,
the control circuit executing the voltage application process after executing the erase process and before executing the write process.
6. The semiconductor memory device according to claim 1 ,
the control circuit applying the first voltage and the second voltage a plurality of times to the ferroelectric film in the voltage application process.
7. The semiconductor memory device according to claim 6 ,
the control circuit alternately applying the first voltage and the second voltage in the voltage application process.
8. The semiconductor memory device according to claim 1 ,
the ferroelectric film including hafnium (Hf) and oxygen (O) as main components, and, including at least one of silicon (Si), magnesium (Mg), aluminum (Al), barium (Ba), zirconium (Zr), gadolinium (Gd), lanthanum (La), samarium (Sm), nitrogen (N) and yttrium (Y) as additive.