The thermal stability of thin (<= 110 nm) compressively strained Ge surface channels, grown by reduced-pressure chemical vapor deposition on high quality relaxed Si0.2Ge0.8 reverse-graded buffers, has been investigated using in-situ hydrogen annealing at temperatures up to 650 degrees C. Strain relaxation was observed and found to increase for thicker channels and higher anneal temperatures. For a Ge channel thickness <= 45 nm, an increased surface roughening was found to dominate the strain relaxation process, which culminated in islanding. For the thicker (>= 45 nm) Ge channels misfit dislocation generation appeared to be the most dominant mechanism. Our results show that low thermal budgets (T < 550 degrees C) should be employed for the fabrication of similar to 0.65% lattice mismatch strained Ge channels currently being developed for applications in CMOS-based devices and strained Ge-on-insulator platforms. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.063205jes] All rights reserved.