Method of operating semiconductor memory device with floating body transistor using silicon controlled rectifier principle

• US 8,837,247 B2
• Filed: 09/10/2013
• Issued: 09/16/2014
• Est. Priority Date: 08/05/2008
• Status: Active Grant

• Current Assignee: Zeno Semiconductor, Inc.
• Original Assignee: Zeno Semiconductor, Inc.
• Inventors: Widjaja, Yuniarto
• Primary Examiner(s): LE, TOAN K
• Application Number:
  US14/023,246
• Publication Number:
  US 20140021549A1
• Time in Patent Office: 371 Days
• Field of Search: 365/222, 365/189.011, 365/174, 365/189.03, 257/E29.255
• US Class Current: 365/222
• CPC Class Codes: G11C 11/404 with one charge-transfer gate, e.g. MOS transistor, per cell
• CPC Class Codes: G11C 11/406 Management or control of the refreshing or charge-regeneration cycles
• CPC Class Codes: G11C 11/4076 Timing circuits for regeneration management G11C11/406
• CPC Class Codes: G11C 11/4096 Input/output [I/O] data management or control circuits, e.g. reading or writing circuits, I/O drivers or bit-line switches
• CPC Class Codes: G11C 2211/4016 Memory devices with silicon-on-insulator cells
• CPC Class Codes: H01L 29/7841 with floating body, e.g. programmable transistors
• CPC Class Codes: H10B 12/20 DRAM devices comprising floating-body transistors, e.g. floating-body cells

Abstract

An exemplary semiconductor memory cell is provided to include: a floating body region configured to be charged to a level indicative of a state of the memory cell; a first region in electrical contact with the floating body region; a second region in electrical contact with the floating body region and spaced apart from the first region; a gate positioned between the first and second regions; a buried layer region in electrical contact with the floating body region, below the first and second regions, spaced apart from the first and second regions; and a substrate region configured to inject charge into the floating body region to maintain the state of the memory cell; wherein an amount of charge injected into the floating body region is a function of a charge stored in the floating body region.

Claims

1. A semiconductor memory cell comprising:

a floating body region configured to be charged to a level indicative of a state of the memory cell;

a first region in electrical contact with said floating body region;

a second region in electrical contact with said floating body region and spaced apart from said first region;

a gate positioned between said first and second regions;

a buried layer region in electrical contact with said floating body region, below said first and second regions, spaced apart from said first and second regions; and

a substrate region configured to inject charge into said floating body region to maintain said state of the memory cell;

wherein an amount of charge injected into said floating body region is a function of a charge stored in said floating body region.

2. The cell of claim 1, wherein said first region has a first conductivity type selected from a p-type conductivity type and an n-type conductivity type;

said floating body region has a second conductivity type selected from said p-type and n-type conductivity types, said second conductivity type being different from said first conductivity type;

said second region has said first conductivity type;

said buried layer region has said first conductivity type; and

said substrate has said second conductivity type.

3. The cell of claim 1, further comprising insulating layers bounding the side surfaces of said floating body region.

4. The cell of claim 1, further comprising:

a source line terminal electrically connected to one of said first and second regions;

a bit line terminal electrically connected to the other of said first and second regions;

a word line terminal connected to said gate;

a buried well terminal connected to said buried layer; and

a substrate terminal connected to said substrate.

5. The cell of claim 1, wherein said maintaining said state of the memory cell is a non-algorithmic process.

6. The cell of claim 1, wherein applying a voltage to said substrate region offsets charge leakage out of said floating body.

7. The cell of claim 6, wherein said voltage applied to said substrate region is a constant positive voltage bias.

8. The cell of claim 6, wherein said voltage applied to said substrate region is a periodic pulse of positive voltage.

9. The cell of claim 6, wherein said floating body region and first and second regions are formed in a fin that extends above said buried layer, said gate is provided on opposite sides of said fin, between said first and second regions, and said floating body region is between said first and second regions.

10. The cell of claim 6, wherein said floating body region and said first and second regions are formed in a fin that extends above said buried layer, said gate is provided on opposite sides and adjacent to a top surface of said fin, between said first and second regions, and said floating body region is between said first and second regions.

11. A semiconductor memory cell comprising:

a floating body region configured to be charged to a level indicative of a state of the memory cell;

a first region in electrical contact with said floating body region;

a second region in electrical contact with said floating body region and spaced apart from said first region;

a gate positioned between said first and second regions;

a buried layer region in electrical contact with said floating body region, below said first and second regions, spaced apart from said first and second regions; and

a substrate region positioned below said buried layer region;

wherein applying a voltage to said substrate region results in at least two stable floating body charge levels.

12. The memory cell of claim 11, wherein said voltage applied to said substrate region is a constant positive voltage bias.

13. The memory cell of claim 11, wherein said voltage applied to said substrate region is a periodic pulse of positive voltage.

14. A semiconductor memory array comprising:

a plurality of said memory cells arranged in a matrix of rows and columns, wherein each said semiconductor memory cell includes;

a floating body region configured to be charged to a level indicative of a state of the memory cell;

a first region in electrical contact with said floating body region;

a second region in electrical contact with said floating body region and spaced apart from said first region;

a gate positioned between said first and second regions;

a buried layer region in electrical contact with said floating body region, below said first and second regions, spaced apart from said first and second regions; and

a substrate region;

wherein said substrate region is commonly connected to at least two of said memory cells, and wherein said substrate region is configured to inject charge into said floating body region of each of said memory cells connected thereto, to maintain said state of the memory cells in parallel.

15. The semiconductor memory array of claim 14, wherein said substrate region is commonly connected to all of said cells in said array.

16. The semiconductor memory array of claim 14, wherein said substrate region is segmented to allow independent control of bias applied on a selected portion of said memory array.

17. The semiconductor memory array of claim 14, wherein application of voltage to said substrate region maintains the current states of each said memory cell connected thereto.

18. The semiconductor memory array of claim 17, wherein said application of voltage is applied as a constant positive voltage bias.

19. The semiconductor memory array of claim 17, wherein said application of voltage is applied as a periodic pulse of positive voltage bias.

20. The semiconductor memory array of claim 17, wherein a maximum potential that can be held by any of said memory cells connected to said substrate region is a function of said application of voltage to said substrate region.