We experimentally demonstrate high optical quality factor silica microdisk resonators on a silicon chip with large wedge angles by reactive ion etching. For 2-μm-thick microresonators, we have achieved wedge angles of 59°, 63°,70°, and 79° with optical quality factors of 2.4 × 10~7, 8.1 × 10~6, 5.9 × 10~6, and 7.4 × 10~6, respectively, from ～80 μm diameter microresonators in the 1550 nm wavelength band. Also, for 1-μm-thick microresonators, we have obtained an optical quality factor of 7.3 × 10~6 with a wedge angle of 74°. We experimentally demonstrate high optical quality factor silica microdisk resonators on a silicon chip with large wedge angles by reactive ion etching. For 2-μm-thick microresonators, we have achieved wedge angles of 59 °, 63 °, 70 °, and 79 ° with Optical quality factors of 2.4 × 10-7, 8.1 × 10-6, 5.9 × 10-6, and 7.4 × 10-6, respectively, from ~80 μm diameter microresonators in the 1550 nm wavelength band. Also, for 1-μm -thick microresonators, we have obtained an optical quality factor of 7.3 × 10 ~ 6 with a wedge angle of 74 °.