High energy interaction of heavy ions with silicon integrated circuits contribute to transient events or single event effects (SEE) when ionizing the device along the particle path. Knowledge of the electron-hole pair density in the ion track is necessary for studying collected charge and estimating device reliability for deep sub-micron transistors. We have simulated ion-tracks in silicon with a Monte-Carlo code, TRAMOS, which is reported in this paper. High velocity heavy ion interactions with silicon are described within the plane wave Born approximation. For electrons, differential cross-sections are calculated using the phase shift method for elastic collisions and the BEB model for inelastic interactions. Calculations show that for high ion velocities, a non-negligible fraction of the energy is deposited outside the sensitive volume of sub-micron transistors when compared to the case of the low ion velocities. The response of a silicon on insulator transistor to different ion tracks (size, density) is investigated with device simulations. Results show that for the 0.25 lm gate length transistor simulated, due to the technology used, the size of the ion track has minor effect on the collected charge Q c . For ions with same stopping power and different velocities, differences on Q c may show up, due to recombination mechanisms.