In a process of manufacturing a semiconductor device, after a gate oxide film
is formed, the thickness of the gate oxide film is measured by measuring an exposure
period defined from a time at which the oxide film is formed to a time at which
the thickness of the oxide film is measured. In addition, if necessary, the measurement
of the oxide film is corrected to determine the real thickness based on the exposure
period. Accordingly, the thickness of the gate oxide film can be measured accurately.
