Low-temperature direct bonding is a promising method to integrate two or more dissimilar materials into one composite without large thermal stresses. In this paper, we describe a bonding process for silicon and quartz glass via vacuum ultraviolet/ozone (VUV/O-3) activation and a multistep, low-temperature annealing process. A strong bonding strength and a bonding interface without any microcracks were obtained after annealing at 200 degrees C. The surfaces and bonding interface were characterized. After the organic contaminants were removed by VUV/O-3, the treated surfaces were very hydrophilic. In addition, the VUV/O-3-induced surface oxidation increased, resulting in oxide asperities on the substrates. These newly generated surface asperities might possess a strong deformability based on the water stress corrosion effect, leading to gap closure after low-temperature annealing. Moreover, a model for the mechanism of the VUV/O-3-activated bonding was proposed.