To provide a semiconductor device having a thin-film BOX-SOI structure and capable of realizing a high-speed operation of a logic circuit and a stable operation of a memory circuit. A semiconductor device according to the present invention includes a semiconductor support substrate, an insulation layer having a thickness of at mast 10 nm, and a semiconductor layer. In an upper surface of the semiconductor layer, a first field-effect transistor including a first gate electrode and constituting a logic circuit is formed. Further, in the upper surface of the semiconductor layer, a second field-effect transistor including a second gate electrode and constituting a memory circuit is formed. At least three well regions having different conductivity types are formed in the semiconductor support substrate. In the presence of the well regions, a region of the semiconductor support substrate below the first gate electrode and a region of the semiconductor support substrate below the second gate electrode are electrically separated from each other.