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Flanged Trench Capacitor Cell

IP.com Disclosure Number: IPCOM000040323D
Original Publication Date: 1987-Oct-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 2 page(s) / 46K

Publishing Venue

IBM

Related People

Scheuerlein, RE: AUTHOR

Abstract

A one-device dense dynamic random-access memory (DRAM) cell with a low leakage storage node is described. A DRAM cell with its storage node inside a trench collects a considerable charge leakage from the bulk silicon due to charges flowing on the trench surface. High energy minority carriers on the trench surface tend to flow to the cell's diffused node, causing the cell's storage node to be discharged. By introducing a buried oxide layer 10 from the drain side 11 of a field-effect transistor (FET) and extending it part way across the channel region 12 towards the source 13, as shown in Fig. 1, the drain side of the structure is partially protected from the bulk silicon 14 leakage.

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Flanged Trench Capacitor Cell

A one-device dense dynamic random-access memory (DRAM) cell with a low leakage storage node is described. A DRAM cell with its storage node inside a trench collects a considerable charge leakage from the bulk silicon due to charges flowing on the trench surface. High energy minority carriers on the trench surface tend to flow to the cell's diffused node, causing the cell's storage node to be discharged. By introducing a buried oxide layer 10 from the drain side 11 of a field-effect transistor (FET) and extending it part way across the channel region 12 towards the source 13, as shown in Fig. 1, the drain side of the structure is partially protected from the bulk silicon 14 leakage. The equipotential field effect 15 in the drain region is modified by the presence of the buried oxide layer so as to affect the bulk electron flow in the drain region. A vector analysis of an electron 16 in the bulk silicon being attracted to the drain region shows a lateral bias which causes the flow to be in the direction of the arrow 17. This prevents a majority of the electrons from reaching the drain and discharging the storage node 18. The structure can be fabricated in several ways; however, the preferred way is to laterally grow epitaxial (epi) silicon over the silicon dioxide (SiO2) regions, as shown in Fig. 2. The initial structure is patterned with a layer of SiO2 20 on a substrate 21 with a trench 22 which has been insulated 23, filled with pol...