US Patent 9806173 Channel-last replacement metal-gate vertical field effect transistor

A method of making a vertical transistor includes forming a doped source on a substrate; depositing a sacrificial gate material on the source; forming a trench in the sacrificial gate material to expose the doped source; growing an epitaxial layer within the trench to form a channel region extending from the doped source and through the sacrificial gate material; performing an epitaxial growth process to grow an epitaxial layer on a portion of the channel region to form a drain over the sacrificial gate material; depositing a dielectric material on the drain to form a spacer that protects the epitaxial growth; and removing the sacrificial gate material and replacing the sacrificial gate material with a gate stack that surrounds the channel region between the doped source and the drain.