Semiconductor device and manufacturing method thereof

A semiconductor device comprising:

• a substrate having thereon a first region including a polarity inversion layer for reversing polarity between a state in which a crystal grows with Group-III polarity and a state in which a crystal grows with Group-V polarity, and a second region in which the polarity inversion layer is not formed on the substrate;
• a first semiconductor layer which is constituted by a first nitride semiconductor epitaxially grown in a c-axis direction and which is formed on the substrate having the first region and the second region;
• a second semiconductor layer which is constituted by a second nitride semiconductor epitaxially grown in the c-axis direction and having different polarization, electron affinity, and band gap from the first nitride semiconductor, the second semiconductor layer being formed on the first semiconductor layer and forming a heterojunction with the first semiconductor layer;
• a first field-effect-transistor of first electrical-conductivity type including a gate electrode, a source electrode, and a drain electrode and being formed in the first region;
• and
• a second field-effect-transistor of second electrical-conductivity type including a gate electrode, a source electrode, and a drain electrode and being formed in the second region.