FIELD SHIELD TRENCH ISOLATION STRUCTURE FOR GIGA-BIT DRAM

摘要

PURPOSE: An improved field shield trench isolation structure is provided for a dynamic random access memory of giga-bit. CONSTITUTION: A dynamic random access memory(DRAM) formed on a semiconductor body(10) such as a substrate or a chip includes pairs of memory cells, each memory cell having a storage trench, a source region(40) adjoining the storage trench, and a common drain region(42). An inner surface of the storage trench is partially covered with a thin silicon oxide(13) and a thick silicon oxide(15), and the storage trench is filled with polysilicon(14) and silicon oxide(16). A vertical isolating trench(20) is self-aligned with edges of the storage trenches, surrounding a region including the cell, and isolating the cell from each other and from an auxiliary circuit. A sidewall of the isolating trench(20) is at least partially covered with a field shield dielectric layer(21) and a spacer(22). Additionally, the isolating trench(20) is filled with a field shield polysilicon in a lower part and a silicon dioxide in an upper part.