PURPOSE: To increase two-dimensional electron gas concentration and to increase carrier mobility by so simply modifying as to insert an Inlays layer, an Inks layer itself having large Inks composition ratio into an Inlays channel layer.

CONSTITUTION: A GaAs. buffer layer 2, an Inlays channel layer 3, an Inks channel layer 9, an Inlays channel layer 3, an AlGaAs carrier supply layer 4, a GaAs cap layer 5 are sequentially laminated on a semi-insulating GaAs substrate 1. A contact of the layer 5 is provided and a source electrode 6, a drain electrode 7 arranged at an interval are provided. A gate electrode 8 in contact with the AlGaAs carrier supply layer between the electrodes 6 and 7 is provided. Thus, a hetero structure of high quality is provided, and excellent low noise characteristics are obtained.