Trench-gated power MOSFET with protective diode

US6140678A · kind A · utility

Assignee

• SILICONIX INCORPORATED · US

Inventors

• Wayne B. Grabowski · Los Altos, US
• Richard K. Williams · Cupertino, US
• Mohamed N. Darwish · Campbell, US

Key dates

• Filing date: Nov 3, 1997
• Grant date: Oct 31, 2000
• Expiry date: Nov 3, 2017

Classification

• Technology area (CPC H): Electricity
• CPC primary: H10D62/127

Abstract

A power MOSFET includes a trenched gate which defines a plurality of MOSFET cells. A protective diffusion is created, preferably in an inactive cell, so as to form a diode that is connected in parallel with the channel region in each of the MOSFET cells. The protective diffusion, which replaces the deep central diffusion taught in U.S. Pat. No. 5,072,266, prevents impact ionization and the resulting generation of carriers near the corners of the gate trench, which can damage or rupture the gate oxide layer. Moreover, the diode can be designed to have a breakdown voltage which limits the strength of the electric field across the gate oxide layer. The elimination of a deep central diffusion permits an increase in cell density and improves the on-resistance of the MOSFET. Specifications for a number of commercially acceptable devices are given.