Insulated-gate vertical field-effect transistor with high current drive and minimum overlap capacitance

US5122848A · kind A · utility

Assignee

• Micron Technology, Inc. · US

Inventors

• Ruojia Lee · Boise, US
• Fernando Gonzalez · Boise, US

Key dates

• Filing date: Apr 8, 1991
• Grant date: Jun 16, 1992
• Expiry date: Apr 8, 2011

Classification

• Technology area (CPC H): Electricity
• CPC primary: H10D30/63

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 portion 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 ba…