Semiconductor memory device
View Patent ↗In order to latch and store a word line reset level voltage (negative voltage) which is set during reset operation, a word line driver includes PMOS transistors and NMOS transistors. The word line driver further includes a stress-reducing PMOS transistor and an NMOS transistor, and also a word line bias control circuit which controls and activates a supply bias during setting of a word line, start of resetting, and a reset period.
1. A semiconductor memory device comprising:
word line drivers configured to be selected based on a plurality of word line select address signals,
wherein
each of the word line drivers has a set level which is a first voltage, and a reset level which is a second voltage, and
a latch is formed in each of the word line drivers only when a corresponding word line is not selected, and the latch is used to hold the voltage of the word line at the reset level.
2. The semiconductor memory device of claim 1 , wherein
the second voltage is lower than a ground voltage.
3. The semiconductor memory device of claim 1 , wherein
the first voltage is higher than a third voltage which is a maximum voltage of a bit line.
4. The semiconductor memory device of claim 1 , wherein
a portion of the plurality of word line select address signals is connected to a logic which resets all the word lines during a predetermined period of time that a power supply is activated.
5. The semiconductor memory device of claim 1 , wherein
the word line drivers each include a transistor configured to pull down the corresponding word line to the second voltage, and
the threshold voltage of the pull-down transistor is higher than the threshold voltages of the other transistors included in the word line driver.
6. The semiconductor memory device of claim 1 , wherein
the word line drivers each include a transistor configured to pull down the corresponding word line to the second voltage, and
the pull-down transistor includes a plurality of transistors connected in series.
7. The semiconductor memory device of claim 1 , wherein
the word line drivers each include a first and a second PMOS transistor and a first NMOS transistor,
the drain of the first PMOS transistor, the drain of the first NMOS transistor, and the gate of the second PMOS transistor are connected to the corresponding word line,
the gate of the first PMOS transistor, the gate of the first NMOS transistor, and the drain of the second PMOS transistor are commonly connected, and
the source of the first PMOS transistor is connected to a voltage supply for the set level of the corresponding word line, the source of the second PMOS transistor is connected to the first voltage, and the source of the first NMOS transistor is connected to the second voltage.
8. The semiconductor memory device of claim 7 , wherein
the word line drivers each further include a second NMOS transistor,
a first signal is supplied to the gate of the second NMOS transistor, and a second signal is supplied to the source of the second NMOS transistor, and
the drain of the second NMOS transistor is connected to the drain of the second PMOS transistor.
9. The semiconductor memory device of claim 7 , wherein
the word line drivers each further include a third PMOS transistor and a third NMOS transistor,
the third PMOS transistor is connected between the drain of the first PMOS transistor and the gate of the second PMOS transistor,
the third NMOS transistor is connected between the gate of the first NMOS transistor and the drain of the second PMOS transistor, and
the gate of the third PMOS transistor is connected to a ground voltage, and the gate of the third NMOS transistor is connected to the first voltage.
10. The semiconductor memory device of claim 9 , wherein
the word line drivers each further include a second NMOS transistor,
a first signal is supplied to the gate of the second NMOS transistor, and a second signal is supplied to the source of the second NMOS transistor, and
the drain of the second NMOS transistor is connected to the drain of the second PMOS transistor.
11. The semiconductor memory device of claim 7 , further comprising:
a word line bias control circuit including a fourth and a fifth PMOS transistor,
wherein
the source of the fourth PMOS transistor is connected to the first voltage, and the source of the fifth PMOS transistor is connected to a fourth voltage, and
the drain of the fourth PMOS transistor and the drain of the fifth PMOS transistor are connected to the source of the first PMOS transistor.
12. The semiconductor memory device of claim 11 , wherein
the fourth voltage is lower than the first voltage and is higher than a ground voltage.
13. The semiconductor memory device of claim 12 , wherein
the fourth voltage is equal to the third voltage.
14. The semiconductor memory device of claim 11 , wherein
the word line bias control circuit further includes a fourth NMOS transistor,
the source of the fourth NMOS transistor is connected to a ground voltage, and
the drain of the fourth NMOS transistor is connected to the drains of the fourth and fifth PMOS transistors.
15. The semiconductor memory device of claim 1 , wherein
the word line drivers each include a transistor configured to pull up the corresponding word line to a predetermined voltage, and
when the word line driver activates the word line, the first voltage is supplied to the pull-up transistor, and when the word line is inactivated, a voltage lower than the first voltage is supplied to the pull-up transistor.
16. The semiconductor memory device of claim 1 , wherein
the word line drivers each include a transistor configured to pull up the corresponding word line to a predetermined voltage, and
the semiconductor memory device further includes a section configured to selectively supply the first voltage, a ground voltage, or an intermediate voltage between the first voltage and the ground voltage, to the pull-up transistor.
17. The semiconductor memory device of claim 16 , wherein
the ground voltage is supplied to the pull-up transistor only during a predetermined period of time after start of resetting of the word line.
18. The semiconductor memory device of claim 17 , wherein
the pull-up transistor has a substrate node connected to the source thereof.