An etch stop layer is formed over a semiconductor fin and gate stack. The etch stop layer is formed utilizing a series of pulses of precursor materials. A first pulse introduces a first precursor material to the semiconductor fin and gate stack. A second pulse introduces a second precursor material, which is turned into a plasma and then directed towards the semiconductor fin and gate stack in an anisotropic deposition process. As such, a thickness of the etch stop layer along a bottom surface is larger than a thickness of the etch stop layer along sidewalls.