# US 7,745,294 B2 · Methods of manufacturing trench isolated drain extended MOS (demos) transistors and integrated circuits therefrom > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,745,294 B2 - Document ID: US7745294B2 - Status: Granted - Kind: B2 - Application number: 12/268,370 - Filed: 2008-11-10 - Published: 2010-05-13 - Granted: 2010-06-29 - Earliest claimed: 2008-11-10 - Assignees: Texas Instruments Incorporated - Inventors: Sameer Prakash Pendharkar; Binghua Hu - Web page: https://patentgrep.com/patent/US7745294B2 ## CPC - H10D 84/017: {Manufacturing their source or drain regions, e.g. silicided source or drain regions} - H10D 30/0281: {of lateral DMOS [LDMOS] FETs} - H10D 30/65: Lateral DMOS [LDMOS] FETs - H10D 62/116: {adjoining the input or output regions of field-effect devices, e.g. adjoining source or drain regions} - H10D 62/157: {Impurity concentrations or distributions} - H10D 84/038: {using silicon technology, e.g. SiGe} - H10D 64/516: {the thicknesses being non-uniform} - H10D 84/0191: {Manufacturing their doped wells} - H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES ## Abstract A method of fabricating an integrated circuit (IC) including at least one drain extended MOS (DEMOS) transistor and ICs therefrom includes providing a substrate having a semiconductor surface, the semiconductor surface including at least a first surface region that provides a first dopant type. A patterned masking layer is formed on the first surface region, wherein at least one aperture in the masking layer is defined. The first surface region is etched to form at least one trench region corresponding to a position of the aperture. A dopant of a first dopant type is implanted to raise a concentration of the first dopant type in a first dopant type drift region located below the trench region. After the implanting, the trench region is filled with a dielectric fill material. A body region is then formed having a second dopant type in a portion of the first surface region. A gate dielectric is then formed over a surface of the body region and the first surface region. A patterned gate electrode layer is formed over the gate dielectric, a source region in the body region and a drain region in the first surface region on a side of the trench region opposite to the source are formed, and fabrication of the IC is completed. ## Claims ### Claim 1 A method of fabricating an integrated circuit including at least one drain extended MOS (DEMOS) transistor, comprising: providing a substrate having a semiconductor surface, said semiconductor surface comprising at least a first surface region that provides a first dopant type; forming a patterned masking layer on said first surface region, wherein at least one aperture in said masking layer is defined; etching said first surface region to form at least one trench region corresponding to a position of said aperture; implanting a dopant of said first dopant type to raise a concentration of said first dopant type in a first dopant type drift region of said first surface region located below said trench region; after said implanting, filling said trench region with a dielectric fill material; forming a body region having a second dopant type in a portion of said first surface region; forming a gate dielectric over a surface of said body region and said first surface region; forming a patterned gate electrode layer over said gate dielectric; forming a source region of said first dopant type in said body region; and forming a drain region of said first dopant type in said first surface region on a side of said at least one trench region opposite to said source region. ### Claim 2 (depends on 1) The method of claim 1, further comprising forming a dielectric liner layer on a surface of said trench region before said implanting. ### Claim 3 (depends on 2) The method of claim 2, wherein said dielectric liner layer comprises a thermal silicon oxide that is between 75 and 500 Angstroms thick. ### Claim 4 (depends on 1) The method of claim 1, wherein said at least one drain extended MOS transistor comprises a drain extended NMOS transistor; said first dopant type comprises an n-type dopant; and said second dopant type comprises a p-type dopant. ### Claim 5 (depends on 4) The method of claim 4, wherein said implanting comprises implanting an n-type dopant in a dose range of from 1×1011 cm−2 to 1×1012 cm−2 at an energy sufficient to place a projected range of said n-type dopant in said first dopant type drift region. ### Claim 6 (depends on 5) The method of claim 5, wherein said n-type dopant comprises As or Sb. ### Claim 7 (depends on 5) The method of claim 5, wherein said n-type dopant comprises As, said dose range is between 2×1011 cm−2 and 8×1011 cm−2 and said energy is between 120 to 200 keV. ### Claim 8 (depends on 1) The method of claim 1, wherein said patterned masking layer comprises a hard mask layer, said hard mask layer providing the sole masking during said implanting and wherein said implanting comprises blanket implanting. ### Claim 9 (depends on 1) The method of claim 1, wherein said semiconductor surface comprises said first surface region providing said first dopant and a second surface region providing said second dopant; said at least one drain extended MOS transistor comprises at least one drain extended NMOS transistor formed in said first surface region; and at least one drain extended PMOS transistor is formed in said second surface region. ### Claim 10 A method of fabricating an integrated circuit including at least one drain extended MOS (DEMOS) transistor, comprising: providing a substrate having a semiconductor surface, said semiconductor surface comprising at least a first surface region that provides a first dopant type; forming a patterned masking layer on said first surface region, wherein at least one aperture in said masking layer is defined; etching said first surface region to form at least one trench region corresponding to a position of said aperture; forming a dielectric liner layer on a surface of said trench region; implanting a dopant of said first dopant type through said dielectric liner layer to raise a concentration of said first dopant type in a first dopant type drift region of said first surface region located below said trench region; after said implanting, filling said trench region with a dielectric fill material; forming a body region having a second dopant type in a portion of said first surface region; forming a gate dielectric over a surface of said body region and said first surface region; forming a patterned gate electrode layer over said gate dielectric; forming a source region of said first dopant type in said body region; and forming a drain region of said first dopant type in said first surface region on a side of said trench region opposite to said source region. ### Claim 11 (depends on 10) The method of claim 10, wherein said implanting comprises implanting As in a dose range between 2×1011 cm−2 and 8×1011 cm−2 and an energy between 120 to 200 keV. ### Claim 12 (depends on 10) The method of claim 10, wherein a concentration of said first dopant type is at least five times greater at said first surface region below said trench region than at said first surface regions below said gate dielectric. ### Claim 13 (depends on 10) The method of claim 10, wherein said dielectric liner layer comprises a thermal silicon oxide that is between 75 and 500 Angstroms thick. ### Claim 14 (depends on 10) The method of claim 10, wherein said semiconductor surface comprises said first surface region providing said first dopant and a second surface region providing said second dopant; said at least one drain extended MOS transistor comprises at least one drain extended NMOS transistor formed in said first surface region; and at least one drain extended PMOS transistor is formed in said second surface region. ### Claim 15 (depends on 10) The method of claim 10, wherein said at least one drain extended MOS transistor comprises a drain extended NMOS transistor; said first dopant type comprises an n-type dopant; and said second dopant type comprises a p-type dopant. ### Claim 16 (depends on 15) The method of claim 15, wherein said implanting comprises implanting As in a dose range between 2×1011 cm−2 and 8×1011 cm−2 and an energy between 120 to 200 keV. ### Claim 17 (depends on 16) The method of claim 16, wherein a concentration of said first dopant type is at least five times greater at said first surface region below said trench region than at said first surface regions below said gate dielectric. ### Claim 18 (depends on 17) The method of claim 17, wherein said dielectric liner layer comprises a thermal silicon oxide that is between 75 and 500 Angstroms thick. ### Claim 19 A method of fabricating an integrated circuit including at least one drain extended NMOS (DENMOS) transistor, comprising: providing an n-type surface region in a semiconductor surface; forming a trench region in the first dopant type surface region; forming a dielectric liner layer on a surface of the trench region; performing an Rdson reduction implantation of n-type dopant through the dielectric liner layer to raise a concentration of the n-type dopant in an n-type drift region of the n-type surface region below the trench region; following the Rdson reduction implantation, filling the trench region with dielectric fill material; forming a p-type body region in a portion of the n-type surface region spaced from the trench region; forming a gate dielectric over the p-type body region and over the n-type surface region between the p-type body region and the filled trench region; forming a patterned gate electrode layer over the gate dielectric and over the filled trench region; forming an n-type source region in the body region; and forming an n-type drain region in the n-type surface region on a side of the trench region opposite to the source region.