An ideal static induction transistor (ISIT) structure was fabricated using molecular layer epitaxy (MLE). The doping method of MLE enabled us to achieve a sufficiently high level of doping for ISIT fabrication. In the fabrication process a low growth temperature was very important for the device structure, which requires very sharp dopant profiles. For the ISIT, two MLE processes, namely source-drain growth and gate regrowth, were required. The electrical characteristics of the sourcedrain were changed after heat treatment at a temperature higher than 4808C. The effect of the redistribution of dopants of the source-drain structure (n ++ -i-p ++ -i-n + ) during gate regrowth was clearly shown by SIMS (secondary ion mass spectroscopy) measurements for various temperatures of heat treatment. As a result the doped Se diffused from the n ++ source region to the other layers and the doped Zn diffused from the p ++ layer to the i-layers. The source was a heavily Se-doped layer at the doping level of 2-3 ร ร ร 10 19 cm ร3 containing a larger amount of interstitial Se atoms in the lattice. The redistribution of Se from the heavily doped region was detectable even after heat treatment at 4808C for 30 min. For the p ++ layer the profile of the C-doped layer was stable even after heat treatment at 6208C for 30 min, but the profile of Zn changed markedly after heat treatment at 4808C for 30 min. In addition, the carbon-doped p ++ layer acted as a gettering layer for diffused interstitial Se from the source region. The driving force of the redistribution of dopants results in the electric field in the device structures. *