The present disclosure describes an exemplary replacement gate process that forms spacer layers in a gate stack to mitigate time dependent dielectric breakdown (TDDB) failures. For example, the method can include a partially fabricated gate structure with a first recess. A spacer layer is deposited into the first recess and etched with an anisotropic etchback (EB) process to form a second recess that has a smaller aperture than the first recess. A metal fill layer is deposited into the second recess.