A method of forming a semiconductor device includes forming a dielectric layer over a substrate. The method includes forming a layer set over the dielectric layer, wherein the layer set comprises a plurality of layers. The method further includes forming a bottom antireflective coating (BARC) layer over the layer set. The method further includes etching the layer set to form a tapered opening in the layer set, wherein etching the layer set comprises etching at least one layer comprising a silicon-rich photoresist material layer and a second material layer different from the silicon-rich photoresist material, and the tapered opening has sidewalls at an angle with respect to a top surface of the dielectric layer. The method further includes etching the dielectric layer using the layer set as a mask to form an opening in the dielectric layer, wherein etching the dielectric layer comprises reducing a thickness of the layer set.