US Patent 9437503 Vertical FETs with variable bottom spacer recess

A method of forming a variable spacer in a vertical transistor device includes forming a first source/drain of a first transistor on a substrate; forming a second source/drain of a second transistor on the substrate adjacent to the first source/drain, an isolation region arranged in the substrate between the first source/drain and the second source/drain; depositing a spacer material on the first source/drain; depositing the spacer material on the second source/drain; forming a first channel extending from the first source drain and through the spacer material; forming a second channel extending from the second source/drain and through the spacer material; wherein the spacer material on the first source/drain forms a first spacer and the spacer material on the second source/drain forms a second spacer, the first spacer being different in thickness than the second spacer.