Vertical wrap-around-gate field-effect-transistor for high density, low voltage logic and memory array
First Claim
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1. A method of fabricating a vertical semiconductor transistor, said method comprises:
- providing a semiconductor substrate;
forming a polysilicon pillar on the substrate;
using the thickness of a first film layer to define a first source/drain region of the transistor as the top portion of the pillar;
forming a spacer layer around the top portion of the pillar;
using the thickness of a second film layer to define a channel region of the transistor as the central portion of the pillar and to align a transistor gate with the channel region of the transistor;
depositing a dielectric layer on the pillar in alignment with the channel region of the transistor;
forming the transistor gate in alignment with the channel region of the transistor, wherein the transistor gate is formed to surround the pillar with the dielectric layer between a conductive material and the pillar;
using the thickness of the spacer layer around the top portion of the pillar to define the thickness of the transistor gate, a top portion of the transistor gate being underneath a bottom portion of the spacer layer; and
defining a second source/drain region of the transistor as the bottom portion of the pillar using the thickness of a third film layer.
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Abstract
A vertical transistor having a wrap-around-gate and a method of fabricating such a transistor. The wrap-around-gate (WAG) vertical transistors are fabricated by a process in which source, drain and channel regions of the transistor are automatically defined and aligned by the fabrication process, without photolithographic patterning.
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Citations
18 Claims
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1. A method of fabricating a vertical semiconductor transistor, said method comprises:
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providing a semiconductor substrate; forming a polysilicon pillar on the substrate; using the thickness of a first film layer to define a first source/drain region of the transistor as the top portion of the pillar; forming a spacer layer around the top portion of the pillar; using the thickness of a second film layer to define a channel region of the transistor as the central portion of the pillar and to align a transistor gate with the channel region of the transistor; depositing a dielectric layer on the pillar in alignment with the channel region of the transistor; forming the transistor gate in alignment with the channel region of the transistor, wherein the transistor gate is formed to surround the pillar with the dielectric layer between a conductive material and the pillar; using the thickness of the spacer layer around the top portion of the pillar to define the thickness of the transistor gate, a top portion of the transistor gate being underneath a bottom portion of the spacer layer; and defining a second source/drain region of the transistor as the bottom portion of the pillar using the thickness of a third film layer. - View Dependent Claims (2, 3, 4, 5)
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6. A method of fabricating a semiconductor structure containing at least one vertical transistor, the method comprising the acts of:
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providing a substrate wherein at least a portion of the working surface thereof is polysilicon; depositing first, second and third material layers on the substrate; forming at least one hole through the material layers over the polysilicon portion of the substrate surface to thereby expose the polysilicon; epitaxially growing a respective polysilicon pillar from the polysilicon portion of the substrate surface through each of the at least one hole; forming a protective cap layer over each pillar; removing the third material layer to thereby expose the sidewall surface of a top portion of each pillar; forming a spacer layer around the top portion of each pillar on the exposed sidewall surface thereof; removing the second material layer to thereby expose the sidewall surface of a central portion of each pillar, the central portion being adjacent and beneath the spacer layer; depositing a dielectric layer around the central portion of each pillar on the exposed sidewall surface thereof; and surrounding the dielectric layer of each pillar with a layer of conductive material. - View Dependent Claims (7, 8, 9, 10, 11)
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12. A method of fabricating a semiconductor structure containing at least one vertical transistor, the method comprising the steps of:
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providing a substrate having a silicon layer disposed over an insulator layer; patterning the silicon layer to form M digit lines, wherein M is a positive integer; depositing a plurality of material layers over the substrate; forming an M×
N array of holes aligned over the M digit lines, wherein N is a positive integer and N holes are formed along each digit line and are aligned with the holes formed over adjacent digit lines;epitaxially growing a respective polysilicon pillar from the polysilicon portion of the substrate surface through each hole; forming a protective cap layer over each pillar; exposing a sidewall surface of a top portion of each pillar; forming a spacer layer around the top portion of each pillar on the exposed sidewall surface; exposing the sidewall surface of a central portion of each pillar; depositing a dielectric layer around the central portion of each pillar on the exposed sidewall surface; and surrounding the dielectric layer of each pillar with a layer of conductive material. - View Dependent Claims (13, 14, 15, 16, 17, 18)
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Specification