Semiconductor structure and methods of fabrication thereof are provided which includes, for instance, providing a carbon-doped material layer within a recess of a semiconductor structure; removing, in part, carbon from the carbon-doped material layer to obtain, at least in part, a carbon-depleted region thereof, the carbon-depleted region having a modified etch property with an increased etch rate compared to an etch rate of the carbon-doped material layer; and recessing the carbon-depleted region of the carbon-doped material layer by an etching process, with the carbon-depleted region being recessed based upon, in part, the modified etch property of the carbon-depleted region.