High aspect ratio gate structure formation

Abstract

A method includes forming a fin over a substrate, forming an isolation structure on the substrate, and forming first and second mandrel patterns over the fin. The fin extends upwardly through the isolation structure. The fin extends lengthwise along a first direction, and each of the first and second mandrel patterns extends lengthwise along a second direction perpendicular to the first direction. The method also includes depositing a sacrificial feature between the first and second mandrel patterns, removing the first and second mandrel patterns, forming a spacer layer in physical contact with sidewalls of the sacrificial feature, removing the sacrificial feature to form a trench, and forming a metal gate stack in the trench. The sacrificial feature extends lengthwise along the second direction.