RuO2 thin films deposited by reactive DC sputtering were heat-treated in a 0.3%-H-2 atmosphere at 200 degrees C in order to investigate the reduction property of RuO2. The films were selectively reduced (starting from the interface) because of insufficient oxidation. When the as-deposited RuO2/Si structure was hydrogen-reduced, the RuO2 film was broken into fragments because of poor mechanical strength. On the other hand, the RuO2 film heat-treated once in O-2 at 700 degrees C cracked into a star shape as a result of vapor generation and volume shrinkage. The star-shape cracking was still observed even when the RuO2 film was covered with a 90-nm-thick BST film. The mechanical strength and the adhesion of RuO2 were improved to some extent by post-oxidation at high temperatures. However, a way to prevent the morphological destruction could not be found because of the thermodynamic equilibrium during the hydrogen reduction process.