Grain growth of ⟨100⟩ textured Ge films on amorphous SiO2substrates during 900 °C isothermal annealing was observed by transmission electron microscopy. An rf sputtering technique was used to deposit the films. By using initially ⟨100⟩ textured film, grain growth (∼1.5 &mgr;m diameter) occurs and is enhanced (∼2 &mgr;m diameter) by square‐wave‐shape grooves fabricated on a SiO2surface, although initial films are relatively thick (0.6 &mgr;m). On the other hand, this grooving edge also has an effect of interrupting the grain growth. These grain growths can be explained by the minimization of the energy required for grain rotation (rotational energy) during grain coalescence.