Memory device comprising electrically floating body transistor

• US 9,831,247 B2
• Filed: 07/25/2016
• Issued: 11/28/2017
• Est. Priority Date: 03/09/2013
• Status: Active Grant

• Current Assignee: Zeno Semiconductor, Inc.
• Original Assignee: Zeno Semiconductor, Inc.
• Inventors: Han, Jin-Woo, Widjaja, Yuniarto
• Primary Examiner(s): NGO, NGAN V
• Application Number:
  US15/218,287
• Publication Number:
  US 20160336326A1
• Time in Patent Office: 491 Days
• CPC Class Codes: G11C 11/404 with one charge-transfer gate, e.g. MOS transistor, per cell
• CPC Class Codes: G11C 11/407 for memory cells of the field-effect type
• CPC Class Codes: G11C 16/00 Erasable programmable read-only memories G11C14/00 takes precedence
• CPC Class Codes: G11C 16/0416 comprising cells containing a single floating gate transistor and no select transistor, e.g. UV EPROM
• CPC Class Codes: H01L 29/0649 Dielectric regions, e.g. SiO2 regions, air gaps
• CPC Class Codes: H01L 29/7841 with floating body, e.g. programmable transistors
• CPC Class Codes: H01L 29/7885 Hot carrier injection from the channel
• CPC Class Codes: H10B 12/20 DRAM devices comprising floating-body transistors, e.g. floating-body cells
• CPC Class Codes: H10B 43/35 with cell select transistors, e.g. NAND

Abstract

A semiconductor memory cell comprising an electrically floating body. A method of operating the memory cell is provided.

Claims

1. A semiconductor memory device comprising:

a memory cell comprising;

a floating body region configured to be charged to a level indicative of a state of the memory cell selected from at least first and second states;

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 first insulating region located above said floating body region;

second insulating regions adjacent to said floating body region;

a buried layer region located below said floating body region and said second insulating regions and spaced from said second insulating regions so as not to contact said second insulating regions; and

a third region in electrical contact with said buried layer region; and

a substrate region different from said third region and underlying said buried layer region;

wherein said floating body region is bounded by said first insulating region above said floating body region, said second insulating regions adjacent to said floating body region, and a depletion region formed as a result of an application of a back bias to said buried layer region.

2. The semiconductor memory device of claim 1, wherein said buried layer region is positioned between said substrate region and said floating body region.

3. The semiconductor memory device 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 second region has said first conductivity type;

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

said buried layer region has said first conductivity type; and

said third region has said first conductivity type.

4. The semiconductor memory device of claim 1, wherein said back bias is applied as a constant positive voltage bias.

5. The semiconductor memory device of claim 1, wherein said buried layer region is configured to inject charge into or extract charge out of said floating body region to maintain said state of the memory cell.

6. A semiconductor memory array comprising at least two memory cells, wherein each said memory cell comprises:

a floating body region configured to be charged to a level indicative of a state of the memory cell selected from at least first and second states;

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 first insulating region located above said floating body region;

second insulating regions adjacent to said floating body region;

a buried layer region located below said floating body region and said second insulating regions;

a third region in electrical contact with said buried layer region; and

a substrate region different from said third region and underlying said buried layer region;

wherein at least one of said floating body regions is integral with or connected to another of said floating body regions; and

wherein said array further comprises a third region in electrical contact with said buried layer region.

7. The semiconductor memory array of claim 6, wherein each said memory cell further comprises a substrate region, wherein said buried layer region is positioned between said substrate region and said floating body region.

8. The semiconductor memory array of claim 6, wherein said first region has a first conductivity type selected from a p-type conductivity type and an n-type conductivity type;

said second region has said first conductivity type;

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

said buried layer region has said first conductivity type; and

said third region has said first conductivity type.

9. The semiconductor memory array of claim 6, wherein said buried layer region is configured to inject charge into or extract charge out of said floating body region to maintain said state of the memory cell.

10. A semiconductor memory array comprising at least two memory cells, wherein each said memory cell comprises:

a floating body region configured to be charged to a level indicative of a state of the memory cell selected from at least first and second states;

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 first insulating region located above said floating body region;

second insulating regions adjacent to said floating body region; and

a buried layer region located below said floating body region and said second insulating regions,

wherein at least one of said floating body regions is integral with or connected to another of said floating body regions;

wherein a depletion region formed as a result of an application of a back bias to said buried layer region and at least one of said second insulating regions adjacent to said floating body region insulates said memory cell from an adjacent memory cell,

wherein application of said back bias results in at least two stable floating body charge levels; and

wherein said array further comprises a third region in electrical contact with said buried layer region, said third region having a conductivity type the same as a conductivity type of said buried layer.

11. The semiconductor memory array of claim 10, wherein each said memory cell further comprises a substrate region, wherein said buried layer region is positioned between said substrate region and said floating body region.

12. The semiconductor memory array of claim 10, wherein said first region has a first conductivity type selected from a p-type conductivity type and an n-type conductivity type;

said second region has said first conductivity type;

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

said buried layer region has said first conductivity type; and

said third region has said first conductivity type.

13. The semiconductor memory cell of claim 10, wherein said back bias is applied as a constant positive voltage bias.

14. The semiconductor memory cell of claim 10, wherein said buried layer region is configured to inject charge into or extract charge out of said floating body region to maintain said state of the memory cell.