Ultra short transistor channel length dictated by the width of a sidewall spacer

Abstract

An integrated circuit fabrication process is provided for forming a transistor having an ultra short channel length dictated by the width of a sidewall spacer which either embodies a gate conductor for the transistor or is used to pattern an underlying gate conductor. In one embodiment, the sidewall spacers are formed upon and extending laterally from the opposed sidewall surfaces of a sacrificial material. The sidewall surfaces of the sacrificial material are defined by forming the sacrificial material within an opening interposed laterally between vertically extending sidewalls which bound a gate dielectric. An upper portion of the gate dielectric is removed to partially expose the sidewall surfaces arranged at the periphery of the sacrificial material. Polysilicon spacers are formed exclusively upon the sidewall surfaces of the sacrificial material to define a pair of gate conductors having relatively small lateral widths. Portions of the gate dielectric not arranged exclusively beneath the gate conductors may be selectively removed. In another embodiment, sidewall spacers are used to protect select regions of a polysilicon gate material arranged exclusively underneath the spacers from being etched. The sidewall spacers are formed upon and extending laterally from sidewall surfaces arranged at the periphery of an opening which extends through a masking or sacrificial material to an underlying polysilicon gate material. The sidewall spacers are sacrificial in that they are removed from the semiconductor topography after they have served their purpose of masking the underlying polysilicon gate material.