To ensure chemical stability and long-term operation, organic electronic devices require encapsulations with low water vapor transmittance rate. A thermally-grown silicon dioxide, oxidized from single-crystalline silicon wafer at high temperature, has an ultra-low water vapor transmittance rate due to a high density without pinholes and defects. However, the thermally-grown silicon dioxide has low an elastic limit and shows a brittle fracture. For that reasons, it is necessary to improve a stretchability of the thermally-grown silicon dioxide thin film for stretchable encapsulation. Therefore, by applying a wavy structure to the thermally-grown silicon dioxide, we improved the stretchability. We fabricated a wavy structured thermally-grown silicon dioxide by oxidizing wavy textured singlecrystalline silicon wafer. We carried out tensile test and cyclic tensile test by using a nano universal testing machine to analyze the stretchability. Lastly, we discussed about the correlation between the improvement of stretchability and the wavy structure through a FEM analysis.