Dram cell with vertical cmos transistor

Abstract

A DRAM memory cell having a trench capacitor includes a vertical pass transistor formed in the top of the trench in a process that forms a doped poly protective layer on the upper sidewalls above a sacrificial intrinsic poly spacer layer, the doped poly protecting the sidewalls while the intrinsic poly spacer layer is removed and replaced with a conductive strap layer that both forms a strap from the capacitor electrode and serves as a source of dopant to form a transistor electrode in the silicon substrate; the protective layer and the upper portion of the strap material being removed simultaneously so that no extra step is required; after which the trench walls are oxidized to form the transistor gate dielectric and conductive material is deposited to form the wordline and the gates for the vertical transistors simultaneously.