The semiconductor device and the method of fabricating the same includes, on a surface of a semiconductor substrate 1 of a first conductivity type which is P-type or N-type, a diode element using a PN junction including a high-concentration first conductivity type impurity region 6 of the first conductivity type, a high-concentration second conductivity type impurity region 5 of a second conductivity type that is a conductivity type opposite to the first conductivity type, and an element isolation region 2 sandwiched between the high-concentration first conductivity type impurity region and the high-concentration second conductivity type impurity region, and a floating layer 3 of the second conductivity type separated from the high-concentration second conductivity type impurity region below the high-concentration second conductivity type impurity region on the semiconductor substrate.