MOS field-effect transistor formed on the SOI substrate

A semiconductor device comprising:

• a supporting substrate including an upper surface having a first region, second regions sandwiching the first region in a first direction, and third regions sandwiching the first and second regions in the first direction;
• a first insulating film formed on the supporting substrate;
• a first semiconductor layer formed on the first insulating film;
• a gate electrode formed via a gate insulating film on a portion of the first semiconductor layer which is right above the first region;
• a pair of source/drain regions containing an impurity of a first conductivity type, formed so as to sandwich the gate electrode therebetween in the first direction;
• and
• a diffusion layer containing an impurity of a second conductivity type, formed in the second region,
• wherein a concentration of an impurity of the second conductivity type introduced into an upper surface of the supporting substrate is higher in the second regions than the first region,
• wherein the source/drain regions include:
• an extension region, including an impurity of the first conductivity type, formed in a portion of an upper surface of the first semiconductor layer above the second regions, and
• a second semiconductor layer, to which an impurity of the first conductivity type is introduced at a concentration higher than a concentration of the extension region, formed on a portion of the first semiconductor layer above the third regions, and
• wherein a concentration of an impurity of the second conductivity type introduced into the upper surface of the supporting substrate is higher in the second regions than the third regions.