A method of manufacture of a semiconductor device includes forming a gate insulating film and a gate electrode made of polycrystalline silicon over a semiconductor substrate; implanting ions into the semiconductor substrate to form a semiconductor region as a source or drain; forming a cobalt film and a titanium nitride film over the semiconductor substrate to cover the gate electrode; carrying out annealing to cause a reaction between Co and Si and the semiconductor region to form a CoSi layer; carrying out wet cleaning to remove the titanium nitride film and unreacted cobalt film to leave the CoSi layer over the gate electrode and semiconductor region; carrying out annealing to cause a reaction between the CoSi layer and the gate electrode and semiconductor region to form a CoSi2 layer; carrying out HPM cleaning; and forming over the semiconductor substrate a silicon nitride film by low-pressure CVD to cover the gate electrode.