Method of treating an exposed conductive film prior to forming a silicide

A method of manufacturing a semiconductor device includes forming a first conductive film on a semiconductor substrate via a first insulating film; forming a second conductive film on the first conductive film via a second insulating film; patterning the first and the second conductive films and the second insulating film to form a plurality of gate electrodes; filling a third insulating film between the plurality of gate electrodes; exposing an upper portion of the second conductive film by removing the third insulating film; covering surfaces of the exposed upper portion of the second conductive film with fluoride (F) or carbon (C) or oxygen (O); and forming a metal film on an upper surface of the second conductive film; and forming silicide layers on the upper portion of the second conductive films by thermally treating the metal film.