Dynamic RAM cell having shared trench storage capacitor with sidewall-defined bridge contacts and gate electrodes.

摘要

A one-device shared trench memory cell, in which the polysilicon (22,24) and dielectric layers (26,26A) within the trench (20) extend above the surface of the trench to form a mandrel structure. A layer of polysilicon is conformably deposited on the mandrel structure. Dopant ions are diffused from the doped polysilicon within the trench to the conformal polysilicon layer, and from the conformal polysilicon layer to a portion of the substrate disposed thereunder (36). The conformal polysilicon is etched in a solvent that preferentially attacks undoped polysilicon, to provide a bridge contact (30) that is self-aligned to the polysilicon within the trench and to the diffusion region. A plurality of FETs formed on either side of the trench, by use of a sidewall-defined gate electrode (34) to maximize density. The cell produces a "poly-to-poly" and "poly-to-substrate" storage capacitor combination that maximizes charge storage capability.