ance and obtain higher transition frequency and reduce emitter crowding. But on the other hand, this III-82 also increases total-dose sensitivity, the effect is particularly important in interdigitated transistors. This explain why it not uncommon to observe bipolar transistors significantly affected by doses in the range of 100 kilorad(SiO2), and sometimes 10 kilorad(SiO2) only. At larger doses, collector-emitter leakage currents can also possibly appear for very vulnerable NPN transistors. Because of the possible appearance of a surface channel between the collector and a part of the basis, the avalanche voltage VCEO can decrease for NPN transistors. The above discussions primarily deal with vertical transistors, which are ordinarily the most robust. Additionally, it must be noted that commercial (COTS) analog integrated circuits commonly use lateral transistors or substrate PNP transistors (those working with collector built at the surface of silicon like the drain of a MOS transistor) [Emil-96]. These parasitic transistors are generally much more vulnerable, due to the large surface of base exposed to insulator [Schm- 95] [Schm-96], and, due to this enhanced vulnerability, may present large sensitivity to dose-rate and time-related effects [Witz-96]. Improvements can be realized by work on the oxide "spacer". The sensitivity of spacer oxides formed with transition to medium to thick has been pointed out [Johns-96]. On the other hand, there is a tendency to use trenches. Recent developments in the bipolar technology concern the bipolar with epitaxial base SiGe (Bipolar Transistor Heterojunction (HBT) [Hara-95]). This process has as potential the improvement of performances in transition frequency, SO as to compete with GaAs transistor in some extent, with as favorable asset the compatibility of manufacturing lines with silicon ones due to common equipment and compatible chemistry. It has been shown that such devices present remarkable behavior after radiation with degradation of gain less than 20% after total 