Single-step CH4/H-2-based reactive ion etching (RIE) process, without alternating O-2 plasma treatment, has been developed with virtually no polymer buildup on the etched surface. InP ridge waveguides up to 1.9 mu m high were etched without any mid- or post-etch O-2 plasma treatment. Smooth and polymer-free sidewalls led to a slight undercut resulting in sidewall slope of similar to 85 degrees. Very low waveguide propagation losses (0.28 dB/cm) of "shallow" etched waveguides were obtained. The etched surface has a root-mean-square roughness of 0.66 nm. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3532767] All rights reserved.