In formation of a source/drain region of an NMOS transistor, a gate-directional extension region of an N+ block region in an N+ block resist film located under the gate-directional extension region from implantation of an N-type impurity. A high resistance forming region, which is the well region having a possibility for implantation of an N-type impurity on a longitudinal extension of a gate electrode , can be formed as a high resistance forming region narrower than a conventional high resistance forming region . Thus, a semiconductor device having a partially isolated body fixed SOI structure capable of reducing body resistance and a method of manufacturing the same are obtained.