The following steps are carried out: forming a gate electrode on a semiconductor substrate with a gate insulating film interposed therebetween, forming a dummy gate electrode on the semiconductor substrate with a dummy gate insulating film interposed therebetween and forming another dummy gate electrode on the semiconductor substrate with an insulating film for isolation interposed therebetween; forming a metal film on the semiconductor while exposing the gate electrode and covering the dummy gate electrodes; and subjecting the semiconductor substrate to heat treatment and thus siliciding at least an upper part of the gate electrode. Since the gate electrode is silicided and the dummy gate electrodes are non-silicided, this restrains a short circuit from being caused between the gate electrode and adjacent one of the dummy gate electrodes.