Insulated-gate vertical field-effect transistor with high current drive and minimum overlap capacitance
First Claim
1. A method of fabricating an insulated-gate vertical field-effect transistor comprising the steps of:
- a) providing a semiconductor substrate of a first conductivity type having a reference surface;
b) forming a trench in the semiconductor substrate, the trench defining a surface including a mesa at the level of the reference surface, a sidewall, and a base recessed from the reference surface;
c) forming an insulated gate layer on the sidewall;
d) forming a first layer of a second conductivity type in the mesa and a second layer of the second conductivity type in the base of the trench;
e) partially filling the trench with a spacer dielectric layer, by;
depositing a spacer dielectric layer atop the surface of the trench;
planarizing the spacer dielectric layer on the mesa of the trench; and
etching the spacer dielectric layer in the base of the trench to a predetermined thickness;
f) forming a conductive layer along the sidewall of the trench over the insulated gate layer extending from the spacer dielectric layer to the reference surface; and
g) the conductive layer being spaced apart from the second layer of the second conductivity type by the spacer dielectric layer to decrease a parasitic capacitance between the conductive layer and the second layer of the second conductivity type.
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Accused Products
Abstract
An insulated-gate vertical FET has a channel region and gate structure that is formed along the sidewall of trench in a P-type semiconductor substrate. The drain and source regions of the FET are formed in the mesa and the base portions of the trench. All contacts to the gate, drain, and source regions can be made from the top surface of the semiconductor substrate. One or more sidewalls of the trench are oxidized with a thin gate oxide dielectric layer followed by a thin polysilicon deposited film to form an insulated gate layer. A reactive ion etch step removes the insulated gate layer from the mesa and the base portions of the trench. An enhanced N-type implant creates the drain and source regions in the mesa and the base portions of the trench. The trench is partially filled with a spacer oxide layer to reduce gate-to-source overlap capacitance. A conformal conductive polysilicon layer is deposited over the insulated gate layer. A portion of the conductive polysilicon layer is extended above the surface of the trench onto the mesa to form a gate contact. A field oxide covers the entire surface of the FET, which is opened in the mesa to form gate and drain contacts, and in the base to form the source contact.
169 Citations
19 Claims
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1. A method of fabricating an insulated-gate vertical field-effect transistor comprising the steps of:
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a) providing a semiconductor substrate of a first conductivity type having a reference surface; b) forming a trench in the semiconductor substrate, the trench defining a surface including a mesa at the level of the reference surface, a sidewall, and a base recessed from the reference surface; c) forming an insulated gate layer on the sidewall; d) forming a first layer of a second conductivity type in the mesa and a second layer of the second conductivity type in the base of the trench; e) partially filling the trench with a spacer dielectric layer, by; depositing a spacer dielectric layer atop the surface of the trench; planarizing the spacer dielectric layer on the mesa of the trench; and etching the spacer dielectric layer in the base of the trench to a predetermined thickness; f) forming a conductive layer along the sidewall of the trench over the insulated gate layer extending from the spacer dielectric layer to the reference surface; and g) the conductive layer being spaced apart from the second layer of the second conductivity type by the spacer dielectric layer to decrease a parasitic capacitance between the conductive layer and the second layer of the second conductivity type. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method of fabricating an insulated-gate vertical field-effect transistor comprising the steps of:
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a) providing a semiconductor substrate of a first conductivity type having a reference surface; b) forming a trench in the semiconductor substrate, the trench defining a surface including a mesa at the level of the reference surface, a sidewall, and a base recessed from the reference surface; c) forming an insulated gate layer on the sidewall; d) forming a first layer of a second conductivity type in the mesa and a second layer of the second conductivity type in the base of the trench; e) forming a conductor that extends from the mesa of the trench to the base of the trench to ohmically contact the second layer of the second conductivity type; f) partially filling the trench with a spacer dielectric layer; and g) opening the spacer dielectric layer to expose the layer of the second conductivity type at the base of the trench for ohmic contact with the conductor. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16, 17, 18)
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19. A method of fabricating an insulated-gate vertical field-effect transistor comprising the steps of:
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a) providing a semiconductor substrate of a first condustivity type having a reference surface; b) forming a trench in the semiconductor substrate, the trench defining a surface including a mesa at the level of the reference surface, a sidewall, and a base recessed from the reference surface; c) forming an insulated gate layer on the sidewall; d) forming a first layer of a second conductivity type in the mesa and a second layer of the second conductivity type in the base of the trench; e) partially filling the trench with a spacer dielectric layer; f) forming a conductive layer along the sidewall of the trench over the insulated gate layer extending from the spacer dielectric layer to the reference surface; g) the conductive layer being spaced apart from the second layer of the second conductivity type by the spacer dielectric layer to decrease a parasitic capacitance between the conductive layer and the second layer of the second conductivity type; h) opening the spacer dielectric layer to expose the layer of the second conductivity type at the base of the trench; and i) forming a field dielectric layer covering the second layer of the second conductivity type in the base of the trench; j) opening the field dielectric layer above the second layer of the second conductivity type to form a second current node contact; and k) covering the second current node contact with an interconnect line.
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Specification