US Patent 9536980 Gate spacers and methods of forming same

An embodiment device includes a gate stack extending over a semiconductor substrate, a hard mask disposed on a top surface of the gate stack, and a low-k dielectric spacer on a side of the gate stack. A top of the low-k dielectric spacer is lower than an upper surface of the hard mask. The device further includes a contact electrically connected to a source/drain region adjacent the gate stack. The contact extends laterally over the low-k dielectric spacer, and a dielectric material is disposed between the contact and the low-k dielectric spacer. The dielectric material has a higher selectivity to etching than the low-k dielectric spacer.