A semiconductor device capable of reducing a threshold voltage is obtained. The semiconductor device includes a pair of source/drain regions formed on the main surface of a semiconductor region to hold a channel region therebetween, and a gate electrode formed on the channel region through a gate insulating film and including a metal-containing layer arranged in the vicinity of an interface between the gate insulating film and the gate electrode, wherein the metal-containing layer is so formed in the form of dots as to partially cover the surface of the gate insulating film, and the average distance between dots forming the metal-containing layer is set to not more than a diameter of the dot of the metal-containing layer.