Ferroelectric memory device

• US 20040213038A1
• Filed: 12/30/2003
• Published: 10/28/2004
• Est. Priority Date: 01/07/2003
• Status: Active Grant

• Current Assignee: Seiko Epson Corporation (Seiko Group)
• Original Assignee: Seiko Epson Corporation (Seiko Group)
• Inventors: Maruyama, Akira
• Granted Patent: US 6,862,236 B2
• Time in Patent Office: Days
• US Class Current: 365/158
• CPC Class Codes: G11C 11/22 using ferroelectric elements

Abstract

A ferroelectric memory device has a function of protecting data held in memory cells from an unexpected unstable power supply voltage generated when the power is turned on or off, or when reading or writing data, and a function of reducing power consumption during reading or writing of data. The ferroelectric memory device includes a short circuit which is operated when the power is turned on or off, or after reading or writing of data occurs. The short circuit short-circuits all of a voltage supply line for a selected word line, a voltage supply line for an unselected word line, a voltage supply line for a selected bit line and a voltage supply line for an unselected bit line, or short-circuits the voltage supply line for the unselected word line and the voltage supply line for the unselected bit line.

Claims

1. A ferroelectric memory device comprising:

a plurality of word lines disposed in parallel;

a plurality of bit lines disposed in parallel so as to intersect the word lines;

a plurality of ferroelectric memory cells disposed at respective intersecting points of the word lines and the bit lines;

a power supply circuit which generates a plurality of types of voltages including a word voltage and a bit voltage;

a word line driver section which drives the word lines;

a bit line driver section which drives the bit lines;

a plurality of voltage supply lines which supply the plurality of types of voltages to the word line driver section and the bit line driver section from the power supply circuit; and

a short circuit which short-circuits a supply line of the word voltage and a supply line of the bit voltage among the voltage supply lines.

2. The ferroelectric memory device as defined in claim 1, further comprising:

a voltage select circuit which selectively outputs the plurality of types of voltages generated by the power supply circuit to the word line driver section and the bit line driver section,

wherein the voltage supply lines include a plurality of word voltage supply lines which connect the voltage select circuit with the word line driver section, and a plurality of bit voltage supply lines which connect the voltage select circuit with the bit line driver section, and

wherein the short circuit short-circuits at least one of the word voltage supply lines and at least one of the bit voltage supply lines.

3. The ferroelectric memory device as defined in claim 2,

wherein the word voltage supply lines include a first voltage-supply-line for a selected word line among the word lines and a second voltage-supply-line for an unselected word line among the word lines, and

wherein the bit voltage supply lines include a third voltage-supply-line for a selected bit line among the bit lines and a fourth voltage-supply-line for an unselected bit line among the bit lines.

4. The ferroelectric memory device as defined in claim 3,

wherein the voltage select circuit outputs voltages selected from among the plurality of types of voltages generated by the power supply circuit, corresponding to an access operation for the ferroelectric memory cells, to the first voltage-supply-line, the second voltage-supply-line, the third voltage-supply-line, and the fourth voltage-supply-line.

5. The ferroelectric memory device as defined in claim 3,

wherein the short circuit short-circuits all of the word voltage supply lines and the bit voltage supply lines when the power is turned on.

6. The ferroelectric memory device as defined in claim 3,

wherein the short circuit short-circuits all of the word voltage supply lines and the bit voltage supply lines when the power is turned off.

7. The ferroelectric memory device as defined in claim 3,

wherein a data read operation or a data write operation of a selected memory cell among the ferroelectric memory cells is implemented by executing at least one of operations of writing “

0” and

writing “

1”

into the selected memory cell, and

wherein the short circuit short-circuits all of the word voltage supply lines and the bit voltage supply lines after at least one of the operations of writing “

0”

or writing “

1”

has been executed.

8. The ferroelectric memory device as defined in claim 3,

wherein a data read operation or a data write operation of a selected memory cell among the ferroelectric memory cells is implemented by executing at least one of operations of writing “

0” and

writing “

1”

into the selected memory cell, and

wherein the short circuit short-circuits the second voltage-supply-line and the fourth voltage-supply-line during a period between the operations of writing “

0” and

writing “

1”

.

9. The ferroelectric memory device as defined in claim 1,

wherein the short circuit includes a plurality of switch circuits which short-circuit all of the word voltage supply lines and the bit voltage supply lines when a power is turned on.

10. The ferroelectric memory device as defined in claim 1,

wherein the short circuit includes a plurality of switch circuits which short-circuit all of the word voltage supply lines and the bit voltage supply lines when a power is turned off.

11. The ferroelectric memory device as defined in claim 1,

wherein the short circuit includes:

a plurality of first switch circuits which short-circuit all of the word voltage supply lines and the bit voltage supply lines when a power is turned on; and

a plurality of second switch circuits which short-circuit all of the word voltage supply lines and the bit voltage supply lines when a power is turned off, and

wherein each of the second switch circuits is connected in parallel with corresponding one of the first switch circuits.

12. The ferroelectric memory device as defined in claim 1,

wherein a data read operation or a data write operation of a selected memory cell among the ferroelectric memory cells is implemented by executing at least one of operations of writing “

0” and

writing “

1”

into the selected memory cell, and

wherein the short circuit includes a plurality of switch circuits which short-circuit all of the word voltage supply lines and the bit voltage supply lines after at least one of the operations of writing “

0”

or writing “

1”

has been executed.

13. The ferroelectric memory device as defined in claim 1,

wherein a data read operation or a data write operation of a selected memory cell among the ferroelectric memory cells is implemented by executing at least one of operations of writing “

0” and

writing “

1”

into the selected memory cell,

wherein the short circuit includes;

a plurality of first switch circuits which short-circuit all of the word voltage supply lines and the bit voltage supply lines when a power is turned on;

a plurality of second switch circuits which short-circuit all of the word voltage supply lines and the bit voltage supply lines when a power is turned off; and

a plurality of third switch circuits which short-circuit all of the word voltage supply lines and the bit voltage supply lines after at least one of the operations of writing “

0”

or writing “

1”

has been executed, and

wherein each of the first switch circuits is connected in parallel with corresponding one of the second switch circuits and corresponding one of the third switch circuits.

14. The ferroelectric memory device as defined in claim 3,

wherein a data read operation or a data write operation of a selected memory cell among the ferroelectric memory cells is implemented by executing at least one of operations of writing “

0” and

writing “

1”

into the selected memory cell, and

wherein the short circuit includes a third switch circuit which short-circuits the second voltage-supply-line and the fourth voltage-supply-line during a period between the operations of writing “

0” and

writing “

1”

.

15. The ferroelectric memory device as defined in claim 3,

wherein a data read operation or a data write operation of a selected memory cell among the ferroelectric memory cells is implemented by executing at least one of operations of writing “

0” and

writing “

1”

into the selected memory cell,

wherein the short circuit includes;

a plurality of first switch circuits which short-circuit all of the word voltage supply lines and the bit voltage supply lines when a power is turned on;

a plurality of second switch circuits which short-circuit all of the word voltage supply lines and the bit voltage supply lines when a power is turned off; and

a third switch circuit which short-circuits the second voltage-supply-line and the fourth voltage-supply-line during a period between the operations of writing “

0” and

writing “

1”

, and

wherein the third switch circuit is connected in parallel with the first and second switch circuits between the second voltage-supply-line and the fourth voltage-supply-line.