Plasma-enhanced chemical vapor deposited (PECVD) silicon oxide (SiO x ) thin films have been widely used in MEMS to form electrical and mechanical components. In this paper, both the time-independent and the time-dependent plastic responses of the PECVD SiO x films were studied by the instrumented nanoindentation experiments. Our experiments found an enhanced rate-sensitivity and size-effect in the plastic responses of the PECVD SiO x thin films. In addition, the plastic flow behavior is more homogeneous compared with most inorganic glasses and many metallic glasses. The deformation mechanism in the PECVD SiO x thin films is depicted by the shear transformation zone (STZ) based amorphous plasticity theory. The physical origin of the STZ is elucidated and linked with the plastic deformation dynamics.