Study for defect in semiconductors induced by ionizing radiation has become much more sophisticated in this recent year, driven by the current development in the ongoing miniaturization of silicon (Si) semiconductor industry. In this paper, the damage evolution due to Cobalt-60 (Co-60) is being simulated in nanoscale Silicon layer using SRIM (Stopping and Range of Ions in Matter). SRIM is a computer simulation that uses Monte Carlo method and it contains TRIM (The Range of Ions in Matter) calculation. The SRIM-TRIM calculates the range of ions in matter using collisions of ions-atoms. Besides, the radiation tolerance of the silicon layer is compared when its thickness is scaling down to nano dimension. From the findings, it is observed that the penetration of Co-60 ions into the target silicon layer leads to production of lattice defects in the form of vacancies, defect clusters and dislocations. These can alter the material parameters and hence the properties of the devices. The simulation results also show that nanoscale silicon layer features improved radiation robustness against ionizing radiation, in term of displacement damage.