a semiconductor device having active parts made from semiconductor diamond . the active parts include a high doped diamond layer for supplying free carriers and a non - or low doped diamond layer for giving the free carriers a conductive region . the free carriers are transferred from the high doped diamond layer to the non - or low doped diamond layer by diffusion or an applied electric field . since the free carriers move at high speeds in the non - or low doped diamond layer without being scattered by dopant atoms , the semiconductor device is applicable to high frequency devices with stability against a change in temperature .