Method of making a field effect trench transistor having lightly doped epitaxial region on the surface portion thereof

US5532179A · kind A · utility

Assignee

• SILICONIX INCORPORATED · US

Inventors

• Mike F. Chang · Cupertino, US
• Fwu-Iuan Hshieh · Saratoga, US
• Sze-Hon Kwan · Sunnyvale, US
• King Owyang · Atherton, US

Key dates

• Filing date: May 23, 1995
• Grant date: Jul 2, 1996
• Expiry date: May 23, 2015

Classification

• Technology area (CPC H): Electricity
• CPC primary: H10D64/513

Abstract

A DMOS field effect transistor having its gate electrode located in a trench includes a lightly doped epitaxial layer overlying the usual epitaxial layer. The trench penetrates only part way through the upper epitaxial layer which is more lightly doped than is the underlying lower epitaxial layer. The lightly doped upper epitaxial layer reduces the electric field at the bottom of the trench, thus protecting the gate oxide from breakdown during high voltage operation. Advantageously the upper portion of the lightly doped upper epitaxial layer has little adverse effect on the transistor's on resistance.