Semiconductor memory device having a sense amplifier circuit with decreased offset
View Patent ↗A semiconductor memory device having high integration, low power consumption and high operation speed. The memory device includes a sense amplifier circuit having plural pull-down circuits and a pull-up circuit. A transistor constituting one of the plural pull-down circuits has a larger constant than that of a transistor constituting the other pull-down circuits, for example, a channel length and a channel width. The pull-down circuit having the larger constant transistor is activated earlier than the other pull-down circuits and the pull-up circuit, which are activated to conduct reading. The data line and the earlier driven pull-down circuit are connected by an NMOS transistor and the NMOS transistor is activated or inactivated to control the activation or inactivation of the pull-down circuit.
1. A semiconductor device comprising:
a memory array having a plurality of word lines, a plurality of data lines, and a plurality of memory cells arranged at respective intersections of the plurality of word lines and the plurality of data lines, and
a respective sense amplifier circuit connected to each of a plurality of data line pairs of the plurality of the data lines,
wherein the sense amplifier circuit has a first MISFET pair, a second MISFET pair, and a third MISFET pair,
the first and second MISFET pairs are of a first conduction type and the third MISFET pair is of a second conduction type which is opposite to the first conduction type,
a gate of one of the first MISFET pair and one of the data line pairs, which is included in the plurality of data lines and is provided corresponding to a drain of the other of the first MISFET pair, are connected with each other,
a gate of one of the second MISFET pair and a drain of the other of the second MISFET pair are connected with each other,
a gate of one of the third MISFET pair and a drain of the other of the third MISFET pair are connected with each other,
the first MISFET pair includes a first transistor having the first conduction type and a second transistor having the first conduction type,
the drain of the first transistor is connected with the source of a fourth MISFET having the first conduction type,
the drain of the second transistor is connected with the source of a fifth MISFET having the first conduction type,
drains of the fourth and fifth MISFETs are connected to the data line pair, respectively,
the fourth and fifth MISFETs are activated to drive the first MISFET pair preceding to the second MISFET pair and the third MISFET pair, and
the fourth and fifth MISFETs are inactivated before a corresponding one of the plurality of word lines is inactivated.
2. The semiconductor device according to claim 1 , further comprising:
a plurality of column switches connected to each of the plurality of data lines,
wherein the fourth and fifth MISFETs are inactivated before a corresponding one of the plurality of column switches is activated.
3. The semiconductor device according to claim 2 , wherein the fourth and fifth MISFETs are activated again by an identical timing with that of the corresponding one of the plurality of column switches.
4. The semiconductor device according to claim 1 , wherein stand-by gate voltages of the fourth and fifth MISFETs are negative voltages.
5. The semiconductor device according to claim 1 , further comprising:
a sub-word driver driving a corresponding one of the plurality of word lines,
wherein gate electrodes of the fourth and fifth MISFETs are connected to a wiring layer in a region where the sub-word driver and the sense amplifier circuit intersect each other.