A semiconductor device includes a semiconductor layer formed by epitaxial growth in a first region which is obtained by etching a semiconductor substrate to a predetermined depth, a surface of the semiconductor layer having a same height from the bottom of the semiconductor substrate as a height of a surface of the semiconductor substrate, a buried insulating layer buried between the semiconductor substrate and the semiconductor layer and an element isolation region separating each element region in the semiconductor layer and isolating the semiconductor layer from the semiconductor substrate in plan.