# US 2014/0197484 A1 · Dual Work Function Recessed Access Device and Methods of Forming > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0197484 A1 - Document ID: US20140197484A1 - Status: Published application - Kind: A1 - Application number: 14/217,844 - Filed: 2014-03-18 - Published: 2014-07-17 - Earliest claimed: 2006-05-11 - Assignees: Micron Technology, Inc. - Applicants: Micron Technology, Inc. - Inventors: Venkatesan Anathan; Sanh D. Tang - Web page: https://patentgrep.com/patent/US20140197484A1 ## CPC - H10D 30/63: Vertical IGFETs (H10D30/66 {, H10D30/6728, H10D30/689, H10D30/693} take precedence) - H10D 64/027: {by etching at gate locations} - H10D 64/518: {characterised by their lengths or sectional shapes} - H10D 64/667: {the conductor comprising a layer of alloy material, compound material or organic material contacting the insulator, e.g. TiN workfunction layers (having lateral variation H10D64/671)} - H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES ## Abstract A recessed access device having a gate electrode formed of two or more gate materials having different work functions may reduce the gate-induced drain leakage current losses from the recessed access device. The gate electrode may include a first gate material having a high work function disposed in a bottom portion of the recessed access device and a second gate material having a lower work function disposed over the first gate material and in an upper portion of the recessed access device. ## Claims ### Claim at position 1 1-25. (canceled) ### Claim 26 A recessed access device, comprising: semiconductor material having at least one trench therein; a gate dielectric over a surface of the at least one trench; a first gate material lining over only a lowest-most portion of the at least one trench; and a second gate material within the at least one trench over the first gate material lining, the second gate material being of different composition from composition of the first gate material, the second gate material projecting outwardly within the at least one trench relative to the first gate material lining that is over only said lowest-most portion of the at least one trench. ### Claim 27 (depends on 26) The recessed access device of claim 26, wherein that portion of the second gate material that is within the at least one trench contacts the gate dielectric within the at least one trench. ### Claim 28 (depends on 26) The recessed access device of claim 26, wherein the first gate material lining has spaced elevationally outermost surfaces, said spaced elevationally outermost surfaces being planar and elevationally coincident. ### Claim 29 (depends on 26) The recessed access device of claim 26, wherein the first gate material lining has spaced elevationally outermost surfaces, the second gate material being elevationally over said spaced elevationally outermost surfaces. ### Claim 30 (depends on 29) The recessed access device of claim 29, wherein that portion of the second gate material that is within the at least one trench contacts the gate dielectric within the at least one trench. ### Claim 31 (depends on 30) The recessed access device of claim 30, wherein the second gate material contacts said spaced elevationally outermost surfaces. ### Claim 32 (depends on 31) The recessed access device of claim 31, wherein that portion of the second gate material that is within the at least one trench contacts the gate dielectric within the at least one trench. ### Claim 33 (depends on 26) The recessed access device of claim 26, wherein the composition of the first gate material is selected from the group consisting of p-type doped polysilicon, titanium nitride (TiN), tantalum nitride (TaN), tungsten nitride (WN), ruthenium (Ru), molybdenum nitride (MoN), TaN/TiN, WN/TiN, p-type polysilicon/TiN, and combinations thereof. ### Claim 34 (depends on 26) The recessed access device of claim 26, wherein the second gate material has a work function less than or equal to 4.5 eV. ### Claim 35 (depends on 26) The recessed access device of claim 26, wherein the composition of the second gate material is selected from the group consisting of n-doped polysilicon, undoped polysilicon, phosphorus (P) doped polysilicon, arsenic (As) doped polysilicon, tantalum (Ta), aluminum (Al), titanium (Ti), and zirconium nitride (ZrN). ### Claim 36 (depends on 25) The recessed access device of claim 25, further comprising a third gate material within the at least one trench and over the second gate material, the third gate material being of different composition from composition of the first gate material and of different composition from composition of the second gate material. ### Claim 37 A recessed access device, comprising: semiconductor material having an elevationally outermost surface and having at least one trench therein; a gate dielectric over a surface of the at least one trench; a first gate material over at least a portion of the gate dielectric in a bottom portion of the at least one trench and having an elevationally outermost surface within the at least one trench that is elevationally inward of the elevationally outermost surface of the semiconductor material; a second gate material over the first gate material in at least a portion of the at least one trench, the second gate material being of different composition from composition of the first gate material; and a third gate material in at least a portion of the at least one trench over the first gate material and the second gate material, the third gate material contacting the at least a portion of the gate dielectric in the at least one trench, the third gate material being of different composition from composition of the first gate material and of different composition from composition of the second gate material. ### Claim 38 (depends on 37) The recessed access device of claim 37, wherein the second gate material does not contact the gate dielectric. ### Claim 39 (depends on 37) The recessed access device of claim 37, wherein the third gate material has a lower work function than the first work function. ### Claim 40 (depends on 37) The recessed access device of claim 37, wherein the first gate material has a work function greater than or equal to 4.5 eV. ### Claim 41 (depends on 37) The recessed access device of claim 37, wherein the second gate material has a work function less than or equal to 4.5 eV. ### Claim 42 (depends on 37) The recessed access device of claim 37, wherein the composition of the first gate material is selected from the group consisting of p-type doped polysilicon, titanium nitride (TiN), tantalum nitride (TaN), tungsten nitride (WN), ruthenium (Ru), molybdenum nitride (MoN), TaN/TiN, WN/TiN, p-type polysilicon/TiN, and combinations thereof. ### Claim 43 (depends on 37) The recessed access device of claim 37, wherein the composition of the second gate material is selected from the group consisting of n-doped polysilicon, undoped polysilicon, phosphorus (P) doped polysilicon, arsenic (As) doped polysilicon, tantalum (Ta), aluminum (Al), titanium (Ti), and zirconium nitride (ZrN). ### Claim 44 A recessed access device, comprising: semiconductor material having an elevationally outermost surface and having at least one trench therein; a gate dielectric over a surface of the at least one trench; a first gate material within the at least one trench over at least a portion of the gate dielectric in a bottom portion of the at least one trench, the first gate material being formed to be half circle-shaped in a cross section transverse the at least one trench and having a planar elevationally outermost surface within the at least one trench in the cross section that is elevationally inward of the elevationally outermost surface of the semiconductor material, all of the first gate material being received entirely within the at least one trench; and a second gate material overlying at least a portion of the first gate material, the second gate material being of different composition from composition of the first gate material. ### Claim 45 A recessed access device, comprising: semiconductor material having at least one trench therein; a gate dielectric over a surface of the at least one trench, the gate dielectric comprising an arcuate outer surface in a bottom portion of the at least one trench; a first gate material over at least a portion of the gate dielectric in the bottom portion of the at least one trench, the first gate material comprising an arcuate outer surface in a bottom portion of the at least one trench; and a second gate material over the arcuate outer surface of the first gate material in at least a portion of the at least one trench, the second gate material being of different composition from composition of the first gate material, the second gate material having an upper neck portion within the at least one trench and a lower shouldered portion within the at least one trench in a cross section transverse the at least one trench, the upper neck portion being laterally centered relative to the shouldered portion, the upper neck portion in including a portion within the at least one trench that projects elevationally outward of all first gate material that is within the at least one trench. ### Claim 46 (depends on 45) The recessed access device of claim 45 wherein the semiconductor material within which the at least one trench is provided has an elevationally outermost surface proximate the at least one trench, the neck portion of the second gate material being everywhere received elevationally inward of the elevationally outermost surface of the semiconductor material.