Semiconductor device and method for fabricating the same

A method for fabricating a semiconductor device, comprising:

• forming an insulating film including a high-dielectric constant film on a semiconductor substrate;
• forming a first conductive film including an oxide film formed on an upper surface thereof and containing at least one of high melting point metal or a compound thereof on the insulating film;
• forming a second conductive film containing silicon on the first conductive film with the oxide film being interposed therebetween;
• forming a gate electrode including a first gate electrode made of part of the first conductive film, part of the oxide film, and a second gate electrode made of part of the second conductive film, and a gate insulating film made of part of the insulating film;
• forming an impurity-doped layer in regions of the semiconductor substrate positioned below both sides of the gate electrode by performing ion implantation of a conductive impurity using the gate electrode as a mask;
• and
• after the forming the impurity-doped layer, forming the impurity-doped layer into an impurity diffusion layer by performing heat treatment to activate the conductive impurity,
• wherein, in the forming the impurity-doped layer, a constituent material of the oxide film and silicon of the second conductive film are mixed together by the ion implantation, thereby simultaneously forming a mixing layer and the impurity-doped layer, and
• in the forming the impurity-doped layer into the impurity diffusion layer, the impurity diffusion layer is formed by the heat treatment and the mixing layer is formed into a conductive layer.

A semiconductor device, comprising:

• a gate insulating film formed on a semiconductor substrate and including a high-dielectric constant film;
• and
• a gate electrode including a first gate electrode formed on the gate insulating film and containing at least one of high melting point metal or a compound thereof, a second gate electrode formed on the first gate electrode and containing silicon, and a conductive layer formed at an interface between the first and second gate electrodes,
• wherein an oxide of the high melting point metal and silicon are mixed together in the conductive layer.