Memory cell having an electrically floating body transistor and programming technique therefor

• US 7,476,939 B2
• Filed: 10/11/2005
• Issued: 01/13/2009
• Est. Priority Date: 11/04/2004
• Status: Active Grant

• Current Assignee: Micron Technology, Inc.
• Original Assignee: Innovative Silicon ISI SA
• Inventors: Okhonin, Serguei, Nagoga, Mikhail
• Primary Examiner(s): Smith, Zandra V.
• Assistant Examiner(s): Chiu, Tsz K
• Application Number:
  US11/247,727
• Publication Number:
  US 20060091462A1
• Time in Patent Office: 1,190 Days
• Field of Search: 438197-199, 438/243, 438/386, 438/242, 257301-302, 257/347, 257/316, 257/341, 257/354, 257/66, 257/67, 365/185.14
• US Class Current: 257/347
• CPC Class Codes: G11C 11/404 with one charge-transfer gate, e.g. MOS transistor, per cell
• CPC Class Codes: G11C 2211/4016 Memory devices with silicon-on-insulator cells
• CPC Class Codes: H01L 27/1203 the substrate comprising an insulating body on a semiconductor body, e.g. SOI three-dimensional layout H01L27/0688
• CPC Class Codes: H01L 29/7841 with floating body, e.g. programmable transistors
• CPC Class Codes: H01L 29/78654 Monocrystalline silicon transistors
• CPC Class Codes: H10B 12/00 Dynamic random access memory [DRAM] devices

Abstract

A memory cell comprising an electrically floating body transistor including a source region, a drain region, a body region disposed therebetween, wherein the body region is electrically floating, and a gate disposed over the body region and separated therefrom by a gate dielectric. The memory cell includes a first data state representative of a first charge in the body region and a second data state representative of a second charge in the body region wherein the second charge is substantially provided by removing carriers from the body region through the gate. Thus, a memory cell may be programmed to a logic low by, for example, causing, forcing and/or inducing carriers in the floating body of the transistor to tunnel through or traverse the gate dielectric to the gate of the electrically floating body transistor (and, in many array configurations, the word line of a memory cell array).

Claims

1. An integrated circuit comprising:

a semiconductor memory cell comprising an electrically floating body transistor comprising;

a source region;

a drain region;

a body region disposed between the source region and the drain region, wherein the body region is electrically floating; and

a gate disposed over the body region and separated therefrom by a gate dielectric; and

wherein the memory cell includes;

a first data state representative of a first charge in the body region; and

a second data state representative of a second charge in the body region wherein the second charge is substantially provided by removing carriers from the body region through the gate; and

control circuitry, coupled to the memory cell, to generate control signals, including first control signals, to program one of a plurality of data states into the memory cell, wherein, in response to the first control signals applied to the memory cell, the electrically floating body transistor provides the second charge in the body region by removing carriers from the body region through the gate.

2. The integrated circuit of claim 1 wherein the first charge comprises an accumulation of majority carriers in the body region of the transistor.

3. The integrated circuit of claim 1 wherein the second charge is provided in the body region by applying (i) positive voltages to the drain region and source region, and (ii) a negative voltage to the gate.

4. The integrated circuit of claim 1 wherein positive voltages are applied to the drain region and source region to substantially remove at least all carriers of the first charge from the body region through the gate of the transistor.

5. The integrated circuit of claim 1 wherein, in response to the first control signals applied to the gate, drain region and source region, the second charge is substantially provided in the body region by causing, forcing and/or inducing majority carriers in the body region to tunnel through the gate dielectric to the gate of the transistor.

6. The integrated circuit of claim 1 wherein the control circuitry generates second control signals to program the first data state into the memory cell, wherein, in response to the second control signals applied to the memory cell, the electrically floating body transistor provides the first charge in the body region of the electrically floating body transistor, wherein the first charge is provided in the body region via impact ionization or band-to-band tunneling phenomenon.

7. The integrated circuit of claim 1 wherein negative voltages are applied to the drain region and source region and a positive voltage is applied to the gate to provide the second charge in the body region of the transistor.

22. The integrated circuit of claim 1 wherein the memory cell consists essentially of the electrically floating body transistor.

25. The integrated circuit of claim 1 wherein the control circuitry includes means for generating the control signals to program one of a plurality of data states into the memory cell.

8. An integrated circuit comprising:

a semiconductor memory cell array comprising a plurality of dynamic random access memory cells arranged in a matrix of rows and columns, each dynamic random access memory cell comprises a transistor, each transistor comprises;

a source region;

a drain region;

a body region disposed between the source region and the drain region, wherein the body region is electrically floating; and

a gate disposed over the body region and separated therefrom by a gate dielectric; and

wherein each dynamic random access memory cell includes;

a first data state representative of a first charge in the body region of the associated transistor; and

a second data state representative of a second charge in the body region of the associated transistor wherein the second charge is substantially provided by removing carriers from the body region through the gate of the associated transistor; and

control circuitry, coupled to the dynamic random access memory cells, to generate control signals, including first control signals, to program one of a plurality of data states into the memory cells, wherein, in response to first control signals applied to a first plurality of memory cells, the electrically floating body transistor associated with each memory cell of the first plurality of memory cells provides the second charge in the corresponding body region.

9. The integrated circuit of claim 8 wherein a first row of dynamic random access memory cells is adjacent to (i) a second row of dynamic random access memory cells and (ii) a third row of dynamic random access memory cells wherein the source region of the transistor of each memory cell corresponding to the first row of dynamic random access memory cells is connected to a first source line, and wherein the gate of the transistor of each memory cell corresponding to the first row of dynamic random access memory cells is connected to a first word line.

10. The integrated circuit of claim 9 wherein the source region of the transistor of each memory cell corresponding to the second raw of dynamic random access memory cells is connected to the first source line, and wherein the gate of the transistor of each memory cell corresponding to the second row of dynamic random access memory cells is connected to a second word line.

11. The integrated circuit of claim 9 wherein the source region of the transistor of each memory cell corresponding to the second row and the third row of dynamic random access memory cells is connected to a second source line and third source line, respectively, and wherein the gate of the transistor of each memory cell corresponding to the second row and the third row of dynamic random access memory cells is connected to a second word line and a third word line, respectively.

12. The integrated circuit of claim 11 wherein the drain region of the transistor of each memory cell corresponding to the first row of dynamic random access memory cells is the same region as the drain region of the transistor of an adjacent memory cell of the third row of dynamic random access memory cells.

13. The integrated circuit of claim 8 wherein a memory cell of the semiconductor memory cell array is programmed to the second data state by the control circuitry by applying (i) a positive voltage to the drain region of the associated transistor, (ii) a positive voltage to the source region of the associated transistor, and (iii) a negative voltage to the gate of the associated transistor.

14. The integrated circuit of claim 13 wherein in response to (i) the positive voltage to the drain region of the associated transistor, (ii) the positive voltage to the source region of the associated transistor, and (iii) the negative voltage to the gate of the associated transistor, the second charge is substantially provided in the body region of the associated transistor by causing, forcing and/or inducing majority carriers in the floating body of the associated transistor to tunnel through the gate dielectric to the gate of the associated transistor.

15. The integrated circuit of claim 8 wherein the control circuitry generates second control signals to program the first data state into at least one memory cell, wherein, the transistor associated with the at least one memory cell, in response to the second control signals applied to the at least one memory cell, provides the first charge in the electrically floating body region associated therewith via impact ionization or band-to-band tunneling phenomenon.

16. The integrated circuit of claim 8 wherein a memory cell of the semiconductor memory cell array is programmed to the second data state by the control circuitry by applying (i) a negative voltage to the drain region of the associated transistor, (ii) a negative voltage to the source region of the associated transistor, and (iii) a positive voltage to the gate of the associated transistor.

23. The integrated circuit of claim 8 wherein each dynamic random access memory cell consists essentially of the transistor.

26. The integrated circuit of claim 8 wherein the control circuitry includes means for generating the control signals to program one of a plurality of data states into the memory cells.

17. An integrated circuit comprising:

semiconductor memory cell comprising an electrically floating body transistor, disposed in or on a semiconductor region or layer which resides on or above an insulating region or layer of a substrate, the electrically floating body transistor comprising;

a first region having impurities to provide a first conductivity type;

a second region having impurities to provide the first conductivity type,

a body region disposed between the first region, the second region and the insulating region or layer of the substrate, wherein the body region is electrically floating and includes impurities to provide a second conductivity type wherein the second conductivity type is different from the first conductivity type;

a gate spaced apart from the body region and separated therefrom by a gate dielectric; and

wherein the memory cell includes;

a first data state representative of a first charge in the body region of the transistor; and

a second data state representative of a second charge in the body region wherein the second charge is substantially provided by removing carriers from the body region through the gate; and

control circuitry, coupled to the memory cell, to generate control signals, including first control signals, to program one of a plurality of data states into the memory cell, wherein, in response to the first control signals applied to the memory cell, the electrically floating body transistor provides the second charge in the body region of the electrically floating body transistor by removing carriers from the body region through the gate.

18. The integrated circuit of claim 17 wherein the first charge in the body region of the transistor of the memory cell comprises an accumulation of majority carriers and wherein positive voltages are applied to the drain region and source region to substantially remove carriers of at least the first charge from the body region of the transistor through the gate of the transistor.

19. The integrated circuit of claim 17 wherein, in response to the first control signals applied to the gate, drain region and source region of the transistor of the memory cell, the second charge is substantially provided in the body region of the transistor by causing, forcing and/or inducing majority carriers in the body region to tunnel through the gate dielectric to the gate of the transistor.

20. The integrated circuit of claim 17 wherein the control circuitry generates second control signals to program the first data state into the memory cell, wherein, in response to the second control signals applied to the memory cell, the transistor provides the first charge in the body region of the transistor, wherein the first charge is provided in the body region of the transistor of the memory cell via impact ionization or band-to-band tunneling phenomenon.

21. The integrated circuit of claim 17 wherein the memory cell consists essentially of the electrically floating body transistor.

24. The integrated circuit of claim 17 wherein the control circuitry includes means for generating the control signals to program one of a plurality of data states into the memory cell.