FIELD EFFECT TYPE SEMICONDUCTOR DEVICE

PURPOSE:To improve the high frequency characteristic and high speed operation by enhancing mutual conductance and reducing gate capacitance by deeply forming the second region, the third region, and a gate region in this order so that the second region becomes the deepest. CONSTITUTION:Si ions are implanted via a mask of photo resist 12 into one main surface of a semi-insulation GaAs substrate 11, thus forming an N type semiconductor region 13 serving as so-called a channel layer which includes a source and a drain. Next, after removing the mask 12, the substrate 11 is adhered in opposition to another GaAs substrate in H2 gas containing AsH3, and capless annealing treatment is performed. Then, an Si nitride film 14 is adhesion-formed on one main surface of the substrate 11, the part corresponding to the gate part of this Si nitride film 14 is selectively removed by the plasma etching with CF4+O2 gas via a mask of photo resist, resulting in the formation of a window hole 16. Further, a high resistant region (i.e. N type region of a low concentration) 17 is so formed as to be superposed on an N type semiconductor region 13, and a gate region 19 of the second semiconductivity type, i.e., P type is formed by selectively diffusion Zn through the same window hole 16 by the Si nitride film 14.