Embodiments of the present invention generally relates to an apparatus and a method for processing semiconductor substrates. Particularly, embodiments of the present invention relates to methods and apparatus for trench and via profile modification prior to filling the trench and via. One embodiment of the present invention comprises forming a sacrifice layer to pinch off a top opening of a trench structure by exposing the trench structure to an etchant. In one embodiment, the etchant is configured to remove the first material by reacting with the first material and generating a by-product, which forms the sacrifice layer.