a method of forming a semiconductor device structure includes forming an interlevel dielectric layer over a semiconductor substrate and a dummy transistor gate structure formed on the substrate ; infusing a shallow gas cluster ion beam layer in a top portion of the ild layer ; and removing at least one layer from the dummy transistor gate structure , wherein the at least one layer comprises a same material as the ild layer and wherein the gcib layer has a slower etch rate with respect to the ild layer .