Vertical platinum sidewall structures 50 nm thick and 700 nm tall have been fabricated by Pt deposition from the thermal decomposition of tetrakis‐(trifluorophosphine)‐platinum using an effusive gas source followed by ion‐assisted etching. Scanning electron microscope micrographs show that the sidewalls have high uniformity, very fine grains, and very sharp contours, demonstrating a high degree of conformal deposition. Scanning Auger microscopy confirms the presence of platinum only in the sidewalls. X‐ray photoelectron spectroscopy analysis of the as‐deposited platinum film reveals no detectable impurity and Scotch tape test shows good bonding of the film. The method is suitable to large‐scale processing.