To provide a semiconductor device which suppresses body floating effect, and to provide a manufacturing method of the semiconductor device.

A semiconductor device having a silicon on insulator (SOI) structure includes: a silicon substrate 1; an embedded insulation layer 2 formed on the silicon substrate 1; and a semiconductor layer 3 formed on the embedded insulation layer 2. The semiconductor layer 3 has a first conductive type body region 4, a second conductive type source region 5, and a second conductive type drain region 6, and a gate electrode 8 is formed on the body region 4 between the source region 5 and the drain region 6 via a gate oxide film 7. The source region 5 includes a second conductive type extension layer 52 and a silicide layer 51 contacting with the extension layer 52 at a side surface. A crystal defect region 12 is formed in a region of a depletion layer occurring in a boundary portion between the silicide layer 51 and the body region 4.