Disclosed are approaches for forming semiconductor device cavities. One method may include providing a set of semiconductor structures defining an opening, wherein the opening has a first opening width along an upper portion of the opening and a second opening width along a lower portion of the opening, the first opening width being greater than the second opening width. The method may further include forming a blocking layer along the set of semiconductor structures by delivering a material at a non-zero angle of inclination relative to a normal extending perpendicular from a top surface of the set of semiconductor structures. The blocking layer may be formed along the upper portion of the opening without being formed along the lower portion of the opening, and wherein an opening through the blocking layer is present above the opening.