Asymmetric semiconductor memory device having electrically floating body transistor

• US 9,524,970 B2
• Filed: 01/07/2015
• Issued: 12/20/2016
• Est. Priority Date: 03/24/2011
• Status: Active Grant

• Current Assignee: Zeno Semiconductor, Inc.
• Original Assignee: Zeno Semiconductor, Inc.
• Inventors: Widjaja, Yuniarto
• Primary Examiner(s): NGUYEN, DUY T V
• Application Number:
  US14/591,454
• Publication Number:
  US 20150155284A1
• Time in Patent Office: 713 Days
• US Class Current: 1/1
• 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 29/7308 Schottky transistors
• 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

Asymmetric, semiconductor memory cells, arrays, devices and methods are described. Among these, an asymmetric, bi-stable semiconductor memory cell is described that 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 the floating body region; a second region in electrical contact with the floating body region and spaced apart from the first region; and a gate positioned between the first and second regions, such that the first region is on a first side of the memory cell relative to the gate and the second region is on a second side of the memory cell relative to the gate; wherein performance characteristics of the first side are different from performance characteristics of the second side.

Claims

1. An asymmetric semiconductor memory cell comprising:

a floating body region having a first conductivity type selected from n-type conductivity type and p-type conductivity type;

said floating body region comprising means for storing a charge or lack of charge as a volatile memory indicative of a state of the asymmetric semiconductor memory cell;

a first region having said first conductivity type, wherein said first conductivity type of said first region is and being in direct contact with said first conductivity type of said floating body region;

a gate positioned above said floating body region; and

a second region in electrical contact with said floating body region and spaced apart from said first region, said second region having a second conductivity type selected from said n-type and said p-type conductivity type, said second conductivity type being different from said first conductivity type.

2. The asymmetric semiconductor memory cell of claim 1, further comprising:

a substrate; and

a buried layer in said substrate, wherein a portion of said substrate is separated from said floating body region by said buried layer.

3. The asymmetric semiconductor memory cell of claim 1, further comprising:

a silicon-on-insulator substrate; and

a buried insulator layer, wherein said buried insulator layer insulates said silicon-on-insulator substrate from said floating body region.

4. The asymmetric semiconductor memory cell of claim 1, wherein said first region is electrically connected to a gate of a switching transistor to configure connectivity of gates in a field programmable logic array (FPGA).

5. The asymmetric semiconductor memory cell of claim 1, wherein said memory cell is useable as a reference cell by applying an intermediate potential between a first potential indicative of a logic-0 state and second potential indicative of a logic-1 state to said floating body region through said first region.

6. The asymmetric semiconductor memory cell of claim 1, configured for use as a reference cell, further comprising a third region in electrical contact with said floating body region, said third region having said second conductivity type.

7. The asymmetric semiconductor memory cell of claim 6, wherein said third region is located between said gate and said first region.

8. The asymmetric semiconductor memory cell of claim 1, arranged in an array of said semiconductor memory cells comprising at least one row of said cells and a plurality of columns of said cells or at least one column of said cells and a plurality of rows of said cells.

9. An integrated circuit comprising:

a plurality of memory cells arranged in a plurality of rows and a plurality of columns, each said memory cell comprising;

a floating body region having a first conductivity type selected from n-type conductivity type and p-type conductivity type;

said floating body region comprising means for storing a charge or lack of charge indicative of a state of said memory cell;

a first region in electrical contact with said floating body region having a second conductivity type selected from n-type conductivity type and p-type conductivity type, and wherein said second conductivity type is different from said first conductivity type;

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

wherein one of said first region or said second region is connected to a bit line;

a plurality of asymmetric memory cells configured for use as reference cells, each said asymmetric memory cell comprising;

a second floating body region having said first conductivity type;

a third region in electrical contact with said second floating body region having said first conductivity type;

a fourth region in electrical contact with said second floating body region having said second conductivity type and spaced apart from said third region;

wherein said fourth region is connected to a reference bit line; and

a plurality of sensing circuits connected to said bit line and said reference bit line.

10. The integrated circuit of claim 9, further comprising:

a substrate; and

a buried layer in said substrate, wherein said a portion of said substrate is separated from said floating body region by said buried layer.

11. The integrated circuit of claim 9, further comprising:

a silicon-on-insulator substrate; and

a buried insulator layer, wherein said buried insulator layer insulates said silicon-on-insulator substrate from said floating body region.

12. The integrated circuit of claim 10, wherein applying a voltage to said buried layer results in each of said memory cells having at least two stable floating body charge levels.

13. The integrated circuit of claim 9, wherein said sensing circuits compare cell current of at least one of said memory cells to at least one of said asymmetric memory cells.

14. The integrated circuit of claim 9, wherein an intermediate potential between a first potential indicative of a logic-0 state and second potential indicative of a logic-1 state is applied to said second floating body region of said asymmetric memory cell through said third region.

15. The integrated circuit of claim 9, wherein each of said asymmetric memory cells further comprises a fifth region in electrical contact with said second floating body region, said fifth region having said second conductivity type.

16. An integrated circuit comprising:

a plurality of memory cells arranged in a plurality of rows and a plurality of columns, each said memory cell comprising;

a floating body region having a first conductivity type selected from n-type conductivity type and p-type conductivity type;

each said floating body region comprising means for storing a charge or lack of charge indicative of a state of each said memory cell, respectively;

a first region in electrical contact with said floating body region and having a second conductivity type selected from n-type conductivity type and p-type conductivity type, said second conductivity type being different from said first conductivity type; and

a second region in electrical contact with said floating body region, said second region having said second conductivity type and being spaced apart from said first region;

a plurality of asymmetric memory cells configured for use as reference cells, each said asymmetric memory cell comprising;

a second floating body region having a first conductivity type selected from n-type conductivity type and p-type conductivity type;

a third region in electrical contact with said second floating body region and having said first conductivity type;

a fourth region in electrical contact with said second floating body region, said fourth region having said second conductivity type and being spaced apart from said third region;

wherein said third region is connected to a sense line;

a substrate;

a buried layer in said substrate, wherein a portion of said substrate is separated from said floating body region by said buried layer; and

a control circuit configured to provide electrical signals to said buried layer region, wherein said control circuit is connected to said sense line.

17. The integrated circuit of claim 16, wherein said buried layer is connected to at least two of said plurality of memory cells.

18. The integrated circuit of claim 16, wherein applying a voltage to said buried layer results in each of said memory cells having at least two stable floating body charge levels.

19. The integrated circuit of claim 16, wherein said control circuit applies a positive voltage to said buried layer when a potential of said sense line is lower than a reference voltage.

20. The integrated circuit of claim 16, wherein said control circuit applies zero voltage to said buried layer when a potential of said sense line is higher than a reference voltage.