Memory cell for dynamic random access memory (DRAM)

US6383864B1 · kind B1 · utility

Assignee

• Siemens Aktiengesellschaft · DE

Inventors

• Gerd Scheller · Adliswil, CH
• Martin Gall · Kalamazoo, US
• Reinhard Stengl · Stadtbergen, DE

Key dates

• Filing date: Sep 30, 1997
• Grant date: May 7, 2002
• Expiry date: Sep 30, 2017

Classification

• Technology area (CPC H): Electricity
• CPC primary: H10B12/0383

Abstract

A memory cell, which includes a transistor and a capacitor, for use in a DRAM uses a silicon-filled vertical trench as the capacitor and a vertical transistor superposed over the vertical trench in a silicon chip. An epitaxial layer is formed at the top of the fill in the trench to impart seed information to the primarily polysilicon silicon fill in the trench. A polysilicon layer is deposited over the top surface of the chip, is apertured over the top of the trench, and has its sidewalls oxidized. The opening is then refilled with epitaxial silicon in which there is created in operation an inversion layer that serves as the channel of the transistor, and the deposited polysilicon layer serves as the word line. Another silicon layer is deposited over the epitaxial layer to serve as the bit line. The source/drain regions of the transistor are formed at the merger of the deposited layer with the fill in the trench and the merger with the polysilicon layer that serves as the bit line.