The disclosed technology generally relates to forming a semiconductor structure and more particularly to forming a stack of layers of a semiconductor structure using a sacrificial layer that is removed during deposition of a functional layer. In one aspect, the disclosed technology relates to a method of protecting a top surface of a layer in a semiconductor structure. The method comprises: providing the layer on a substrate, the layer having an initial thickness and an initial composition; forming a sacrificial metal layer on and in contact with the layer, the sacrificial metal layer comprising a light metal element; and depositing by physical vapor deposition a functional metal layer on and in contact with the sacrificial metal layer. The sacrificial metal layer is removed by sputtering during the deposition of the functional metal layer, such that an interface is formed between the layer and the functional metal layer. The sacrificial metal layer protects the layer during the deposition of the functional metal layer, such that the layer has a final thickness which substantially matches the initial thickness and a final composition which substantially matches the initial composition.