Abstract: A microcomputer usable for a long period of time even when disposed in a high dose radiation-exposed environment, and its access speed control method are provided. According to the microcomputer and the method, the total dose of radiation that the microcomputer receives is determined on the basis of detection signals from a radiation detecting element. Based on the determined total dose of radiation, and table data preset by tests and stored into a memory unit, a CPU controls an access speed. Moreover, the CPU, and the memory unit and a circuit interface unit that access the CPU are integrated on a single chip (ASIC) These units on the same chip are deteriorated and changed in the same direction, without fail, on exposure to radiation.

Abstract: The present invention intends to provide a radioactive rays detection semiconductor device comprises a substrate, an insulating layer formed on the substrate, p-type Si films formed on the insulating layer and equal in resistance value change rates due to temperature change and different in thickness so as to differ in the changes of the resistance values corresponding to the change of the total dose of the radioactive rays, an insulating film covering the p-type Si films, electrodes deposited in contact holes which are formed in the insulating film to reach both end of the p-type Si films, and Al wiring connecting the electrodes close to each other.