Semiconductor storage device including memory cells, word driver, dummy word driver
A semiconductor storage device includes a plurality of memory cells arranged in a matrix, a word line provided corresponding to a memory cell row, a dummy word line formed in a metal interconnection layer adjacent to a metal interconnection layer in which the word line is formed, a word driver circuit configured to drive the word line, and a dummy word driver circuit configured to increase voltage on the word line based on interline capacitance between the word line and the dummy word line.
1. A semiconductor storage device comprising:
a memory cell formed on a semiconductor substrate;
a word line connected to the memory cell and formed in a first metal interconnection layer located over the semiconductor substrate;
a dummy word line formed in a second metal interconnection layer located over the semiconductor substrate and adjacent to the first metal interconnection layer;
a word driver circuit including a first PMOS (P-type Metal-Oxide-Semiconductor) transistor and a first NMOS (N-type Metal-Oxide-Semiconductor) transistor connected in series between a first power supply voltage and a first ground voltage lower than the first power supply voltage, and supplying the first power supply voltage to the word line corresponding to an address signal;
a dummy word driver circuit including a second PMOS transistor and a second NMOS transistor connected in series between a second power supply voltage and a second ground voltage lower than the second power supply voltage, and supplying the second power supply voltage to the dummy word line;
a first inverter which receives a control signal and outputs an inversion signal of the control signal as a first signal;
a second inverter which receives the first signal and outputs an inversion signal of the first signal as a second signal;
an address decoder which receives the address signal and outputs a decode signal;
a third inverter which receives the decode signal and outputs an inversion signal of the decode signal as a third signal; a first NAND circuit which receives the first signal and the decode signal; and
a second NAND circuit which receives the second signal and the decode signal,
wherein a gate of the first PMOS transistor is connected to an output of the first NAND circuit, and
wherein a gate of the first NMOS transistor is connected to an output of the third inverter,
wherein a gate of the second PMOS transistor and a gate of the second NMOS transistor are connected to an output of the second NAND circuit.
2. The semiconductor storage device according to claim 1 , wherein the dummy word driver circuit further includes a capacitive element provided between the word line and the dummy word line,
wherein the capacitive element has a gate connected to the dummy word line and a source and a drain both connected to the word line.
3. The semiconductor storage device according to claim 1 , wherein the dummy word line is arranged in parallel with the word line.
4. The semiconductor storage device according to claim 1 , wherein the dummy word line and the word line have different lengths.
5. The semiconductor storage device according to claim 1 , wherein at least a partial width of the dummy word line is formed to be thicker than a width of the word line.
6. The semiconductor storage device according to claim 1 , wherein the dummy word line is set to a fixed voltage when the word line is not driven.
7. The semiconductor storage device according to claim 1 , wherein the memory cell is a Static Random Access Memory (SRAM) cell.
8. The semiconductor storage device according to claim 7 , wherein the Static Random Access Memory cell is formed with a fin transistor.
9. The semiconductor storage device according to claim 1 , wherein the word driver circuit sets the word line to a high impedance state when voltage on the word line is increased.
10. The semiconductor storage device according to claim 1 ,
wherein the first power supply voltage and the second power supply voltage have the same voltage value, and
wherein the first ground voltage and the second ground voltage have the same voltage value.
11. The semiconductor storage device according to claim 1 ,
wherein the supply of the first power supply voltage to the word line is cut off by the control signal and the supply of the second power supply voltage to the dummy word line is started corresponding to the control signal.
12. A semiconductor storage device comprising:
a memory cell formed on a semiconductor substrate;
a word line connected to the memory cell and formed in a first metal interconnection layer located over the semiconductor substrate;
a dummy word line formed in a second metal interconnection layer located over the semiconductor substrate and adjacent to the first metal interconnection layer;
a word driver circuit including a first MOS (Metal-Oxide Semiconductor) transistor of a first conductivity type and a second MOS transistor of a second conductivity type connected in series between a first power supply voltage and a first ground voltage lower than the first power supply voltage, and supplying the first power supply voltage to the word line corresponding to an address signal;
a dummy word driver circuit including a third MOS transistor of a first conductivity type and a fourth MOS transistor of a second conductivity type connected in series between a second power supply voltage and a second ground voltage lower than the second power supply voltage, and supplying the second power supply voltage to the dummy word line;
a first inverter which receives a control signal and outputs an inversion signal of the control signal as a first signal;
a second inverter which receives the first signal and outputs an inversion signal of the first signal as a second signal;
an address decoder which receives the address signal and outputs a decode signal;
a third inverter which receives the decode signal and outputs an inversion signal of the decode signal as a third signal;
a first NAND gate circuit which receives the first signal and the decode signal; and
a second NAND gate circuit which receives the second signal and the decode signal,
wherein a gate of the first MOS transistor of the first conductivity type is connected to an output of the first NAND gate circuit, and
wherein a gate of the second MOS transistor of the second conductivity type is connected to an output of the third inverter,
wherein a gate of the third MOS transistor of the first conductivity type and the gate of the fourth MOS transistor of the second conductivity type are connected to an output of the second NAND gate circuit.
13. The semiconductor storage device according to claim 12 ,
wherein the dummy word driver circuit further includes a capacitive element provided between the word line and the dummy word line, and
wherein the capacitive element includes a gate connected to the dummy word line and a source and a drain both connected to the word line.
14. The semiconductor storage device according to claim 12 ,
wherein the first power supply voltage and the second power supply voltage have a same voltage value, and
wherein the first ground voltage and the second ground voltage have a same voltage value.
15. The semiconductor storage device according to claim 12 ,
wherein the supply of the first power supply voltage to the word line is cut off by the control signal and the supply of the second power supply voltage to the dummy word line is started corresponding to the control signal.