TRANSISTOR FOR SUPER-HIGH FREQUENCY AND METHOD OF MANUFACTURING IT

An insulated gate field effect transistor with very small drain capacitance is made by forming as a layer on a substrate of semiconductor material a first region containing impurities of opposite conductivity types with different concentrations and different diffusion characteristics. A recess formed in the first region is filled with semiconductor material by epitaxial growth to form a second region and impurity from the first region is heat diffused into a contiguous portion of the second region to form an intermediate base region the width of which is determined by differences in diffusion distances of the two impurities of opposite type. Also a transistor with a very small collector capacitance is made by masking a surface of a semiconductor body containing impurity of a first conductivity type, forming a window in said mask, hollowing out a recess through the window, partially filling the recess by epitaxial deposit with semiconductor material of the opposite type to form a first region containing a concentration of impurity of the first type with a higher diffusion coefficient than the impurity of the opposite type, epitaxially depositing further material in the recess to form a second region and heat diffusing impurity from said first region into a contiguous portion of said second region to form an intermediate base region the thickness of which is determined by the difference in diffusion distances of the impurities.