The thermal behavior of antifusing device characteristic with SiO2/Ti0.1W0.9 system was investigated. Amelioration and destruction of device properties were found after annealing at 400 degrees C and 600 degrees C, respectively. Through in situ heat treatment at 400 degrees C, it was revealed that metallic tungsten was formed at the interface due to decomposition of WO3. Annealing above 600 degrees C induces decomposition of SiO2 and results in failure of the antifusing device characteristic.