Reliability of a semiconductor device is improved. A p-type MISFET of a thin film SOI type is formed in an SOI substrate including a semiconductor substrate, an insulating layer on the semiconductor substrate, and a semiconductor layer on the insulating layer, and n+-type semiconductor regions which are source and drain region of the p-type MISFET are formed in the semiconductor layer and an epitaxial layer on the semiconductor layer. A semiconductor layer is formed via the insulating layer below the p-type MISFET formed in the n-type well region of the semiconductor substrate. In an n-type tap region which is a power supply region of the n-type well region, a silicide layer is formed on a main surface of the n-type well region without interposing the epitaxial layer therebetween.