PURPOSE: To realize free and well-reproducible control of the impurity distribution of cathode region of a super-stair-case junction part which can not be performed by a conventional method, by repeating epitaxial growth and selective diffusion.

CONSTITUTION: On N+-type Si substrate 11, N epitaxial layer 12 is stacked and SiO2 film 13 is provided with an opening, where N+ layer 14 is formed. It is recommended to use, especially, Sb and As small in diffusion coefficient. After film 13 is removed, epitaxial layer 17 is formed by vapor-phase growth and SiO2 mask 13' is used to form N-type diffusion layer 18 right over layer 14. Under various conditions, layers 14 and 18 can be made N+ layers of complex distribution by combining various impurities. Further, an element with super-staircase junction can be formed by forming P+ layer 15 in the same region. Consequently, mass-production can be realized with good reproducibility and uniformity of various characteristics of a varactor diode.