Method to controllably form notched polysilicon gate structures

Abstract

A method and structure for forming a notched gate structure having a gate conductor layer on a gate dielectric layer. The gate conductor layer has a first thickness. The inventive method includes patterning a mask over the gate conductor layer, etching the gate conductor layer in regions not protected by the mask to a reduced thickness, (the reduced thickness being less than the first thickness), depositing a passivating film over the gate conductor layer, etching the passivating film to remove the passivating film from horizontal portions of the gate conductor layer (using an anisotropic etch), selectively etching the gate conductor layer to remove the gate conductor layer from all regions not protected by the mask or the passivating film. This forms undercut notches within the gate conductor layer at corner locations where the gate conductor meets the gate dielectric layer. The passivating film comprises a C-containing film, a Si-containing film, a Si—C-containing film or combinations thereof.