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US 5,348,905 AGranted
Method of making diffused buried plate trench DRAM cell array
AssigneeInternational Business Machines Corporation
InventorDonald M. Kenney
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Abstract
A high density substrate plate DRAM cell memory device and process are described in which a buried plate region is formed adjacent to deep trench capacitors such that the substrate region of DRAM transfer FETs can be electrically isolated from other FETs on a semiconductor substrate. The buried region is partially formed by lateral outdiffusion from the sidewalls of the deep trenches and partially formed by an N-well surface diffusion which entirely surrounds the DRAM array region.
Claims7
The method of making a dynamic random access memory device comprising the steps of:
- providing a semiconductor substrate of a first conductivity type;
- forming a plurality of deep trenches in a matrix pattern on a top surface of said substrate;
- diffusing a second conductivity type impurity from the lower portion of the depth of said deep trenches into said substrate to form a continuous buried diffused region of a second conductivity type across the entire extent of the matrix pattern;
- forming a dielectric layer on the inside of said deep trenches and filling said trenches with a conductive electrode material;
- forming around the perimeter of said matrix pattern a diffused surface region of said second conductivity type having a depth so as to physically and electrically isolate a portion of the substrate within the matrix pattern above said continuous buried diffused region;
- and
- forming within the isolated portion of the matrix pattern a plurality of semiconductor devices for coupling signals to and from said conductive electrode material within at least some of said deep trenches.
4 more elements
Dependencies are inferred from the claim text.