Super trench MOSFET including buried source electrode and method of fabricating the same

US7183610B2 · kind B2 · utility

Assignee

• SILICONIX INCORPORATED · US

Inventors

• Deva Pattanayak · Saratoga, US
• Yuming Bai · Union City, US
• Kyle Terrill · Santa Clara, US
• Christiana Yue · Milpitas, US
• Robert Xu · Fremont, US
• Kam Hong Lui · Santa Clara, US
• Kuo-In Chen · Los Altos, US
• Sharon Shi · San Jose, US

Key dates

• Filing date: Apr 30, 2004
• Grant date: Feb 27, 2007
• Expiry date: Dec 3, 2024

Classification

• Technology area (CPC H): Electricity
• CPC primary: H10D64/519

Abstract

In a trench MOSFET, the lower portion of the trench contains a buried source electrode, which is insulated from the epitaxial layer and semiconductor substrate but in electrical contact with the source region. When the MOSFET is in an “off” condition, the bias of the buried source electrode causes the “drift” region of the mesa to become depleted, enhancing the ability of the MOSFET to block current. The doping concentration of the drift region can therefore be increased, reducing the on-resistance of the MOSFET. The buried source electrode also reduces the gate-to-drain capacitance of the MOSFET, improving the ability of the MOSFET to operate at high frequencies. The substrate may advantageously include a plurality of annular trenches separated by annular mesas and a gate metal layer that extends outward from a central region in a plurality of gate metal legs separated by source metal regions.