The oxygen radical assisted electron beam (EB) evaporation was employed to prepare SnO2 films with high sensitivity and selectivity to C2H5OH for micro-machined gas sensors. The films deposited by this technique allow a low-temperature and fast annealing process, and therefore has high compatibility to the standard integrated circuit process. The maximum sensitivity is higher than 160, more than 20 times larger than that of films prepared by the conventional EB evaporation, and comparable to that of radio frequency reactive sputtered films. Furthermore, the temperature of maximum sensitivity has also decreased approximately 100 degreesC compared to a conventional EB evaporated SnO2 film.