US Patent 11476346 Vertical transistor having an oxygen-blocking top spacer

Embodiments of the invention are directed to a method of forming a semiconductor device. A non-limiting example of the method includes forming a top spacer trench adjacent to an upper region of the channel fin. An oxygen-blocking layer is deposited within the top spacer trench and over the upper region of the channel fin. A top spacer is formed within the top spacer trench and over a portion of the oxygen-blocking layer that is within the top spacer trench. The oxygen-blocking layer includes an oxygen gettering material.