6F2 access transistor arrangement and semiconductor memory device

• US 7,476,920 B2
• Filed: 12/15/2004
• Issued: 01/13/2009
• Est. Priority Date: 12/15/2004
• Status: Expired due to Fees

• Current Assignee: Polaris Innovations Limited (Wi-LAN Inc.)
• Original Assignee: Infineon Technologies AG
• Inventors: Schloesser, Till
• Primary Examiner(s): Loke; Steven
• Assistant Examiner(s): Khosraviani; Arman
• Application Number:
  US11/011,040
• Publication Number:
  US 20060281250A1
• Time in Patent Office: 1,490 Days
• Field of Search: 257/329, 257331-333, 257/296, 257/295, 257/306
• US Class Current: 257/296
• CPC Class Codes: H01L 21/76232 of trenches having a shape other than rectangular or V-shape, e.g. rounded corners, oblique or rounded trench walls H01L21/76229 takes precedence
• CPC Class Codes: H01L 27/0207 Geometrical layout of the components, e.g. computer aided design; custom LSI, semi-custom LSI, standard cell technique
• CPC Class Codes: H10B 12/05 Making the transistor
• CPC Class Codes: H10B 12/485 Bit line contacts
• CPC Class Codes: H10B 12/50 Peripheral circuit region structures

Abstract

An access transistor arrangement is provided for a 6F² stacked capacitor DRAM memory cell layout with shared bit line contacts. The access transistors are arranged in pairs along semiconductor lines. The two transistors of each pair of transistors are arranged laterally reversed opposing the respective common bit line section. Each pair of access transistors is separated from the adjacent pair of access transistors by an isolation transistor which is permanently turned off. The access transistors and the isolation transistors are formed as identical recessed channel transistors with elongated channel and enhanced isolation properties. The same dopant concentration may be provided for both junctions of the access transistors. As identical devices are provided both as access transistor and as isolation transistors, the complexity of lithographic patterning processes is reduced.

Claims

1. An integrated circuit, comprising:

a first access transistor, a second access transistor, a third access transistor, and a fourth access transistor, each access transistor comprising a gate electrode and an active area, each active area being formed in a substrate and adjacent to a pattern surface of the substrate, each gate electrode being disposed at least in part in a recess groove that is formed in the active area between a respective node contact section and a respective bit line contact section formed within the respective active area, the third access transistor being arranged adjacent to the second access transistor such that the bit line contact sections of the second and third access transistors form a common bit line contact section and such that the active areas of the second and third access transistors form a contiguous semiconductor line;

an isolation transistor arranged between the first and the second access transistors, the first and the second access transistors facing laterally reversed and opposing the isolation transistor, the node contact sections of the first and second access transistors being adjacent to the isolation transistor; and

a further isolation transistor arranged between the third and the fourth access transistors, the third and fourth access transistors facing laterally reversed and opposing the further isolation transistor, the node contact sections of the third and fourth access transistors being adjacent to the further isolation transistor;

wherein the isolation transistors are controllable by isolation gate lines, each isolation gate line being disposed at least in part in an isolation groove and being separated from the substrate by an isolation gate dielectric, the isolation groove being formed in the substrate between the node contact sections of the first and the second access transistors and between the node contact sections of the third and the fourth access transistors.

2. The integrated circuit of claim 1, wherein the recess grooves of the access transistors and the isolation groove have the same shape.

3. The integrated circuit of claim 2, wherein the recess grooves of the access transistors and the isolation groove have the same size.

4. The integrated circuit of claim 1, wherein the recess grooves and the isolation groove are U-shaped.

5. The integrated circuit of claim 1, wherein a turn-off voltage applied to the isolation gate is equal to a voltage applied to the gate electrodes to turn off the access transistors.

6. The integrated circuit of claim 1, wherein the node contact sections and the bit line contact sections are formed as doped regions of a first conductivity type;

channel regions separating the node contact sections and the bit line contact sections in each active area are formed as intrinsic regions or as doped regions of a second conductivity type, wherein the second conductivity type is the opposite of the first conductivity type, and wherein

the node contact sections and the bit line contact sections have the same dopant concentration.

7. The integrated circuit of claim 1, further comprising further semiconductor lines, the semiconductor lines being separated by row insulating lines, wherein the gate electrodes are sections of word lines, and wherein the word lines extend perpendicularly to the semiconductor lines.

17. The integrated circuit of claim 1, wherein the gate electrodes are disposed in part above the pattern surface.

8. A semiconductor memory device, comprising:

a first access transistor, a second access transistor, a third access transistor, and a fourth access transistor, each access transistor comprising a gate electrode and an active area, the active area being formed within a semiconductor substrate;

each active area comprising a bit line contact section, a node contact section and a channel section, the bit line contact section and the node contact section being adjacent to a pattern surface of the substrate, and the channel section separating the bit line contact section and the node contact section; and

each gate electrode being disposed at least in parts in a recess groove formed in the substrate between the respective node contact section and the respective bit line contact section and each gate electrode being separated from the respective channel section by a gate dielectric, the third access transistor being arranged adjacent to the second access transistor such that the bit line contact sections of the second and third access transistors form a common bit line contact section and such that the active areas of the second and third access transistors form a contiguous semiconductor line;

the semiconductor memory device further comprising;

storage capacitors being disposed above the pattern surface, each storage capacitor being coupled to one of the node contact sections;

a bit line, the bit line being coupled to the bit line contact sections; and

an isolation transistor being arranged between the first and the second access transistors, the first and the second access transistors facing laterally reversed and opposing the isolation transistor, the node contact sections of the first and second access transistors being adjacent to the isolation transistor;

a further isolation transistor arranged between the third and the fourth access transistors, the third and fourth access transistors facing laterally reversed and opposing the further isolation transistor, the node contact sections of the third and fourth access transistors being adjacent to the further isolation transistor;

wherein the isolation transistors are controllable by isolation gate lines, each isolation gate line being disposed at least in part in an isolation groove formed in the substrate between the node contact sections of the first and the second access transistors and between the node contact sections of the third and the fourth access transistors and being separated from the substrate by an isolation gate dielectric.

9. The semiconductor memory device of claim 8, wherein the recess grooves of the access transistors and the isolation groove have the same shape.

10. The semiconductor memory device of claim 9, wherein the recess grooves of the access transistors and the isolation groove have the same size.

11. The semiconductor memory device of claim 8, wherein the recess grooves and the isolation groove are U-shaped.

12. The semiconductor memory device of claim 8, wherein a turn-off voltage applied to the isolation gate is equal to a voltage being applied to the gate electrodes to turn off the access transistors.

13. An integrated circuit comprising a semiconductor memory device that comprises:

a plurality of first access transistors and a plurality of second access transistors, each access transistor having a gate electrode and an active area, the active area being formed within a semiconductor substrate;

each active area comprising a bit line contact section, a node contact section and a channel section, the bit line contact section and the node contact section being adjacent to a pattern surface of the substrate and the channel section separating the bit line contact section and the node contact section; and

each gate electrode being disposed at least in part in a recess groove formed in the substrate between the respective node contact section and the respective bit line contact section, and each gate electrode being separated from the respective channel section by a gate dielectric;

the semiconductor memory device further comprising;

a plurality of isolation transistors, each isolation transistor being arranged between a pair of one of the first and one of the second access transistors, the first and the second access transistors facing laterally reversed and opposing the isolation transistor, the node contact section of the first access transistor and the node contact section of the second access transistor being adjacent to the isolation transistor;

a plurality of isolation gate lines of the isolation transistors being separated from the substrate by an isolation gate dielectric layers and being disposed at least in parts in isolation grooves, the isolation grooves being formed in the substrate between the node contact sections of the first and the second access transistors;

wherein a plurality of the access transistors are arranged in lines such that the bit line contact sections of neighboring first and second access transistors form a common bit line contact section and such that the active areas of the access transistors form a contiguous semiconductor line.

14. The integrated circuit of claim 13, wherein the gate electrodes are disposed in part above the pattern surface.

15. The integrated circuit of claim 13, further comprising a plurality of bit lines, wherein each bit line is coupled to contact sections associated with one of the semiconductor lines respectively and sections of the bit line run alternately on opposing sides of the respective semiconductor line.

16. The integrated circuit of claim 13, further comprising a plurality of word lines forming in sections gate electrodes of said plurality of access transistors that are arranged essentially perpendicularly to the semiconductor lines, wherein the word lines are buried completely below the pattern surface.