Computer simulations of fabrication processing p-and n-channel junction field-effect transistor with design norms of 1.5 µm is presented. Corrections to parameters of Klassen mobility model are proposed. They ensure the correspondence between calculated current-voltage characteristics and experimental data. For the investigated device structures of JFET, an analysis of the influence of various types of penetrating radiation on electrical characteristics is carried out. Optimization calculations gave the modes of processing procedure, which reduce the effect of the neutron flux with energy 1.5 MeV on the electrical characteristics of n-JFET device structure by 1.45 times.