We have developed a novel treatment of ZnSe substrates for homoepitaxy using dry etching with a BCl3plasma. The dry‐etched substrates exhibited mirror‐like morphology even after 10‐μm etching in thickness to remove polishing damage, and the quality of its surface was remarkably improved. Subsequent thermal etching of ZnSe was found by reflection high‐energy electron diffraction observation to be valid in the temperature range from 440 to 650 °C. Highest‐quality ZnSe homoepitaxial layer has been obtained by growth on the substrate etched at the BCl3pressure of 60 mTorr. Crystallinity of the layer was as good as that of the dry‐etched substrate. Low‐temperature optical analysis indicated the layer to be high purity and to be free from in‐plane biaxial strain.