US Patent 9916982 Dielectric preservation in a replacement gate process

Structures for use in a replacement gate process involving a field-effect transistor and methods for forming such structures. A first dielectric layer is formed adjacent to a dummy gate structure, and a second dielectric layer is formed on the first dielectric layer. After the second dielectric layer is formed, a portion of the dummy gate structure is removed with an etching process to cut the dummy gate structure into disconnected segments. The second dielectric layer caps the first dielectric layer when the portion of the dummy gate structure is removed. The second dielectric layer has a higher etch rate selectivity than the first dielectric layer to the etching process.