Patent ID: 7759209

Claim:
A method of manufacturing a semiconductor device having an MIS transistor including a silicon substrate, a gate insulating film formed over a main surface of the silicon substrate, a gate electrode including a silicon film formed over the silicon substrate through the gate insulating film, a side wall formed on a side surface of the gate electrode, and diffusion layers formed in the silicon substrate in self-alignment with the side wall, the method comprising the steps of: (a) forming a metal film over the main surface of the silicon substrate so as to cover the gate electrode therewith; (b) after the step (a), reacting the silicon film of the gate electrode with the metal film and also the diffusion layers with the metal film through a first thermal treatment to form first silicide films over an upper portion of the gate electrode and upper portions of the diffusion layers, respectively; (c) after the step (b), removing the metal film left unreacted); and (d) after the step (c), subjecting the first silicide films to phase transformation by a second thermal treatment in an atmosphere containing oxygen to form second silicide films and oxidation products of the metal film on surfaces of the second silicide films, wherein a ratio of oxygen in an atmosphere of the second thermal treatment is larger than a ratio of oxygen in an atmosphere of the first thermal treatment.