This technology relates to high electron mobility transistors (HEMT). In conventional off-type HEMTs, a large amount of gate threshold voltage variation is often found. Transistors according to this technology include a p-type region, a barrier region, an insulation film, a gate electrode, and a channel region. The channel region is connected to an upper surface of the p-type region. The channel region is n-type or i-type and provided with a first channel region and a second channel region. The barrier region is forming a hetero-junction with an upper surface of the first channel region.