A method of removing a hard mask used for patterning gate stacks including patterning gate stacks on a substrate, wherein the hard mask is deposited over the gate stacks. The method further includes depositing a dielectric layer on the substrate after the gate stacks are patterned and planarizing a first portion of the dielectric layer. The method further includes removing a second portion of the dielectric layer and the hard mask by using an etching gas and etching the remaining dielectric layer by using a wet etching chemistry.