We found that both hFE and ICS of the transistors decrease drastically after ion irradiation. The dc current gain (hFE), excess base current (ΔIB = IBpost − IBpre), excess collector current (ΔIC = ICpost − ICpre) and collector-saturation current (ICS) of the ion-irradiated transistors were studied systematically. NPN transistors were irradiated by 95 MeV oxygen ions in a fluence ranging from 5 × 1010 to 5 × 1012 ions cm−2. Understanding of radiation effects on silicon devices has an impact on their design and allows the prediction of a specific device behaviour when exposed to a radiation field of interest. The temporary or permanent damage inflicted by a single particle (single event effect) to electronic devices or integrated circuits is treated separately from the total ionizing dose (TID) effect for which the accumulated fluence causes degradation and from the displacement damage induced by the non-ionizing energy-loss (NIEL) deposition. The particle energy deposition mechanisms by ionization and non-ionization processes are reviewed as well as the radiation-induced damage and its effect on device parameters evolution, depending on particle type, energy and fluence. Some of these fields present adverse radiation environments that may affect the operation of the devices. Silicon and silicon-based devices are commonly operated in many fields including particle physics experiments, nuclear medicine and space. Nowadays, these devices achieving submicron technology are parts of integrated circuits of large to very large scale integration (VLSI). Silicon is used in radiation detectors and electronic devices.