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FET Device with Reduced Overlap Capacitance and Hot Electron Effects

IP.com Disclosure Number: IPCOM000086086D
Original Publication Date: 1976-Jul-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 2 page(s) / 41K

Publishing Venue

IBM

Related People

Beilstein, KE: AUTHOR [+2]

Abstract

Source and drain regions formed in wells or recesses included in a substrate will contribute to reduced overlapped capacitance and hot-electron effects. Reduced overlapped capacitance also contributes to higher circuit density and switching speeds. Trade offs can be made among "effective" junction depth with hot-electron effects, short-channel effects and junction capacitance.

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FET Device with Reduced Overlap Capacitance and Hot Electron Effects

Source and drain regions formed in wells or recesses included in a substrate will contribute to reduced overlapped capacitance and hot-electron effects. Reduced overlapped capacitance also contributes to higher circuit density and switching speeds. Trade offs can be made among "effective" junction depth with hot-electron effects, short-channel effects and junction capacitance.

Shallow junctions are one technique to reduce overlap capacitance. As junctions become shallower and device dimensions are reduced however high- electric field results in the channel region between the source and drain regions. The channel electrons gain high energies and some are injected into the gate insulation, which causes a threshold voltage shift detrimental to operation.

The figure shows a substrate 10 of appropriate conductivity type, an overlying insulating layer 12 and a plurality of wells 14 formed in the substrate, after appropriate masking and etching of the substrate 10 and layer 12. The device is completed by diffusion or implantation into respectively. The insulating layer is regrown between the wells 14 to form the gate insulation 20 after an appropriate opening is made in the layer.

Faster oxide growth over the highly doped regions 16 and 18 leads to the thicker oxide in the well 14 in relation to the oxide 12 for the reasons described in U.S. Patent 3,899,372. Openings 22 and 24 are made over each sourc...