This study proposes an accurate method of monitoring precursor consumption in chemical vapor deposition (CVD) systems. Since precursor costs are significant, finding an efficient method to monitor precursor consumption is necessary. One example is the use of noncontact and inexpensive ultrasonic sensors for determining the liquid level in a container. In this study, sensors based on ultrasonic techniques have been developed for monitoring the precursor consumption in a CVD system. Moreover, the prototype sensors developed in this study can be useful in the field of semiconductors. (c) 2005 American Vacuum Society.