20‐&mgr;m‐thick diamond films deposited on Si single‐crystal substrates by microwave plasma‐enhanced chemical vapor deposition showed significant curvature. The internal stress distribution was estimated using the model of an elastic bimetallic strip. The results indicate that the films are under a mean tensile stress of 1.1 GPa, and are discussed using information from x‐ray diffraction and Raman spectra.