DRAM cell with transfer device extending along perimeter of trench storage capacitor

摘要

A structure and method of manufacture is disclosed herein for a semiconductor memory cell having size of 4.5 F2 or less, where F is the minimum lithographic dimension. The semiconductor memory cell includes a storage capacitor formed in a trench, a transfer device formed in a substantially electrically isolated mesa region extending over a substantial arc of the outer perimeter of the trench, a buried strap which conductively connects the transfer device to the storage capacitor, wherein the transfer device has a controlled conduction channel located at a position of the arc removed from the buried strap. Also disclosed herein are methods of forming a semiconductor memory cell and of forming groups of semiconductor memory cells. A method of forming a semiconductor memory cell includes the steps of forming a storage capacitor in a deep trench etched into a substrate including a monocrystalline semiconductor; forming a shallow trench isolation (STI) region at least partially overlaying the deep trench; forming and outdiffusing a strap in a sidewall of the deep trench; forming first spacers on exterior surfaces of the STI region and deep trench; etching, selective to the monocrystalline semiconductor; removing the first spacers to expose a mesa region of monocrystalline semiconductor located on exterior sidewalls of the deep trench and STI region and conductively connected to the strap; adjusting dopant concentrations in at least a portion of the mesa region to form a channel region and source/drain regions; forming a gate dielectric over at least the channel region; depositing a gate conductor over the channel region; and forming a bitline contact to a first of the source/drain regions.