Impact ionization devices, and methods of forming impact ionization devices
First Claim
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1. An impact ionization device, comprising:
- a pillar vertically extending from an oxide material and comprising;
N+ doped silicon vertically adjacent the oxide material;
undoped epitaxial silicon germanium vertically overlying the N+ doped silicon; and
P+ doped epitaxial silicon germanium vertically adjacent the undoped epitaxial silicon germanium; and
a gate adjacent the pillar and comprising a lower portion laterally adjacent the N+ doped silicon of the pillar and an upper surface vertically separated from a lower boundary of the P+ doped epitaxial silicon germanium of the pillar, the undoped epitaxial silicon germanium of the pillar vertically confined between the lower boundary of the P+ doped epitaxial silicon germanium and the upper surface of the gate.
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Abstract
Impact ionization devices including vertical and recessed impact ionization metal oxide semiconductor field effect transistor (MOSFET) devices and methods of forming such devices are disclosed. The devices require lower threshold voltage than conventional MOSFET devices while maintaining a footprint equal to or less than conventional MOSFET devices.
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Citations
13 Claims
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1. An impact ionization device, comprising:
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a pillar vertically extending from an oxide material and comprising; N+ doped silicon vertically adjacent the oxide material; undoped epitaxial silicon germanium vertically overlying the N+ doped silicon; and P+ doped epitaxial silicon germanium vertically adjacent the undoped epitaxial silicon germanium; and a gate adjacent the pillar and comprising a lower portion laterally adjacent the N+ doped silicon of the pillar and an upper surface vertically separated from a lower boundary of the P+ doped epitaxial silicon germanium of the pillar, the undoped epitaxial silicon germanium of the pillar vertically confined between the lower boundary of the P+ doped epitaxial silicon germanium and the upper surface of the gate. - View Dependent Claims (2, 3, 7, 8, 9, 11, 12, 13)
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4. A method of forming an impact ionization device, the method comprising:
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forming a substrate comprising an oxide material, N+ doped silicon vertically adjacent the oxide material, undoped epitaxial silicon germanium vertically overlying the N+ doped silicon, and P+ doped epitaxial silicon germanium vertically adjacent the undoped epitaxial silicon germanium; removing material of the substrate to form a pillar vertically extending from the oxide material and comprising the N+ doped silicon, the undoped epitaxial silicon germanium, and the P+ doped epitaxial silicon germanium; and forming a gate adjacent the pillar and comprising a lower portion laterally adjacent the N+ doped silicon of the pillar and an upper surface vertically separated from a lower boundary of the P+ doped epitaxial silicon germanium of the pillar, the undoped epitaxial silicon germanium of the pillar vertically confined between the lower boundary of the P+ doped epitaxial silicon germanium and the upper surface of the gate. - View Dependent Claims (5, 6)
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10. An impact ionization device, comprising:
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a pillar vertically extending from an oxide material and comprising; a drain region comprising doped silicon having a first conductivity vertically adjacent the oxide material; an undoped region comprising undoped silicon vertically adjacent the drain region; an impact ionization region comprising undoped silicon germanium vertically adjacent the undoped region; and a source region vertically adjacent the impact ionization region and comprising doped silicon germanium having a second conductivity opposite the first conductivity of the drain region; and a gate flanking opposing lateral surfaces of the pillar, a lower portion of the gate laterally adjacent the drain region, and an upper surface of the gate substantially coplanar with a lower boundary of the undoped silicon germanium of the impact ionization region.
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Specification