pFET nonvolatile memory

• US 8,139,411 B1
• Filed: 01/18/2011
• Issued: 03/20/2012
• Est. Priority Date: 05/22/2008
• Status: Active Grant

• Current Assignee: Synopsys Incorporated
• Original Assignee: Synopsys Incorporated
• Inventors: Pesavento, Alberto
• Primary Examiner(s): TRAN, MICHAEL THANH
• Application Number:
  US13/008,349
• Time in Patent Office: 427 Days
• Field of Search: 365/185.05, 365/185.24
• US Class Current: 365/185.05
• CPC Class Codes: G11C 16/0441 comprising cells containing multiple floating gate devices, e.g. separate read-and-write FAMOS transistors with connected floating gates
• CPC Class Codes: H10B 41/60 the control gate being a doped region, e.g. single-poly memory cell

Abstract

A non-volatile memory integrated circuit includes multiple memory cells, each memory cell including a first MOS transistor, a first control capacitor, and a first floating gate coupled to the first MOS transistor and the first control capacitor. A first read/write control signal is provided having at least a first state and a second state and coupled the first MOS transistor. When the control signal is in the first state, the memory cell is configured for readout, and when the control signal is in the second state, the memory cell is configured for writing. Both single-ended and differential memory cells are described. Arrays of such nonvolatile memory cells are also described.

Claims

1. An integrated circuit comprising one or more columns of memory cells, each column comprising:

one or more memory cells, each memory cell comprising;

a set of floating-gate transistors, each floating-gate transistor comprising a first source connected to a first signal line for receiving a first signal to enable a read operation of each memory cell, a first drain, a first well electrode connected to a second signal line for receiving a second signal applying a voltage to a well region in each of the floating-gate transistor, and a floating gate separated from the first drain and the first source by a gate oxide; and

a set of cell readout transistors, each cell readout transistor comprising a second source connected to the first drain of one of the floating-gate transistors, a second drain, a second well electrode connected to the second signal line, a first non-floating gate connected to a third signal line for receiving a third signal, the third signal in combination with the first and the second signals controlling an operation mode of the memory cell; and

a set of column readout transistors, each column readout transistor comprising a first node connected to the second drain of one of the cell readout transistors, a second non-floating gate connected to a fourth signal line for receiving an inverted version of the third signal, and a second node connected to a data line for reading out data stored in the memory cell.

2. The integrated circuit of claim 1, wherein the floating gate of each of the floating-gate transistors is coupled to a column signal line via a capacitor.

3. The integrated circuit of claim 2, wherein the capacitor comprises a shorted transistor.

4. The integrated circuit of claim 2, wherein the capacitor comprises one of poly-poly capacitor or poly-metal capacitor.

5. The integrated circuit of claim 1, wherein the floating gate transistors are p-type field-effect transistors (FETs).

6. The integrated circuit of claim 5, wherein the cell readout transistors are p-type FETs.

7. The integrated circuit of claim 6, wherein the column readout transistors are n-type FETs.

8. The integrated circuit of claim 1, wherein the set of column readout transistors outputs differential signals at second nodes in a read mode.

9. The integrated circuit of claim 1, wherein the first node is a drain and the second node is a source.

10. The integrated circuit of claim 1, wherein the second signal is shared with at least one other memory cell in a row of memory cells in the integrated circuit.

11. A method for operating a memory cell in an array of memory cells, comprising:

receiving a first signal, for enabling a read operation of the memory cell, at first sources of floating-gate transistors in the memory cell;

receiving a second signal at well electrodes of the floating gate transistors for applying a voltage to well regions in the floating-gate transistors;

receiving a third signal at gates of first readout transistors serially connected to the floating-gate transistors, the third signal in combination with the first and the second signals controlling an operation mode of the memory cell;

receiving an inverted version of the third signal at gates of second readout transistors connected to the first readout transistors serially connected to the first readout transistors; and

outputting data at nodes of the second readout transistors in a read mode defined by the first, second and third signals.

12. The method of claim 11, further comprising:

receiving a first column signal at a floating gate of one of the floating-gate transistor; and

receiving a second column signal at a floating gate of the other floating-gate transistor.

13. The method of claim 11, wherein the floating gate transistors are p-type field-effect transistors (FETs).

14. The method of claim 13, wherein the first readout transistors are p-type FETs.

15. The method of claim 14, wherein the second readout transistors are n-type FETs.

16. The method of claim 11, wherein the data is output from the nodes as differential signals.

17. A memory cell in an integrated circuit, comprising:

a set of floating-gate transistors, each floating-gate transistor comprising a first source connected to a first signal line for receiving a first signal to enable a read operation of the memory cell, a first drain, a first well electrode connected to a second signal line for receiving a second signal applying a voltage to a well region in each of the floating-gate transistor, and a floating gate separated from the first drain and the first source by a gate oxide; and

a set of cell readout transistors, each cell readout transistor comprising a second source connected to the first drain of one of the floating-gate transistors, a second drain, a second well electrode connected to the second signal line, a first non-floating gate connected to a third signal line for receiving a third signal, the third signal in combination with the first and the second signals controlling an operation mode of the memory cell, and wherein each cell readout transistor is connected to one of a column readout transistor in a set of column readout transistors, each column readout transistor in the set comprising a first node connected to the second drain of one of the cell readout transistors, a second non-floating gate connected to a fourth signal line for receiving an inverted version of the third signal, and a second node connected to a data line for reading out data stored in the memory cell.

18. The memory cell of claim 17, wherein the floating gate of each of the floating-gate transistors is coupled to a column signal line via a capacitor.

19. The memory cell of claim 17, wherein the floating gate transistors are p-type field-effect transistors (FETs), the cell readout transistors are p-type FETs, and the column readout transistors are n-type FETs.

20. The memory cell of claim 17, wherein the second signal is shared with at least one other memory cell in a row of memory cells in the integrated circuit.