Semiconductor device and method of fabricating the same

A semiconductor device, comprising:

• a supporting substrate applied with a predetermined potential;
• an insulating layer formed on the supporting substrate;
• a semiconductor layer formed on the insulating layer;
• a first FDSOI transistor formed on the semiconductor layer and including a first source region, a first drain region, and a first channel region, the first channel region being formed between the first source region and the first drain region;
• a first high-concentration impurity region formed in a vicinity of a surface of the supporting substrate at least just below the first channel region;
• a second FDSOI transistor formed on the semiconductor layer and including a second source region, a second drain region, and a second channel region, the second channel region being formed between the second source region and the second drain region;
• and
• a second high-concentration impurity region formed in the vicinity of the surface of the supporting substrate at least just below the second channel region,
• wherein an average impurity concentration in the vicinity of the surface of the supporting substrate just below the first channel region is not lower than an impurity concentration of the first channel region, and
• an average impurity concentration in the vicinity of the surface of the supporting substrate just below the second channel region is not lower than an impurity concentration of the second channel region and is different from the average impurity concentration in the vicinity of the surface of the supporting substrate just below the first channel region.