A method of stably and correctly evaluating impurities distribution under
a gate of a semiconductor device without damaging a silicon substrate is
disclosed. According to the evaluation method, a gate electrode made of a
silicon containing material is removed without removing a gate insulating
film by contacting pyrolysis hydrogen generated by pyrolysis to the
semiconductor device that includes the gate electrode arranged on a
semiconductor substrate through a gate insulating film, and a source
electrode and a drain electrode formed on the semiconductor substrate on
corresponding sides of the gate electrode. Further, a processed form of
the gate is evaluated by observing a form of the gate insulating film
that remains on the semiconductor substrate, the gate insulating film
that remains on the semiconductor substrate is removed by a wet process,
and the impurities distribution under the gate is measured and evaluated.