Cross-sectional transmission electron microscopy observations have been carried out to clarify two-dimensional depth distributions of lattice defects generated in high-dose (5 x 1015 ions/cm2 ), P, As, BF2 and B implanted, annealed submicron Si areas as a function of implantation areas. Monte Carlo simulation is also adapted for ion-implantation into submicron Si through fine mask patterns to predict the effect of mask size on spatial damage and impurity profiles. Simulation results predict that the above profiles have a strong mask size dependence for regions below the critical size, where the dopant concentration decreases and damage depth moves toward the surface-side with a reduced implantation area. Some experimental results support simulation results, although most defects, mainly in the P and As implantation, are confined within the original amorphized layers, independent of mask size. However, in BF2 and B implantation, unexpected defect behavior such as variations in defect distribution from one implanted layer to another is found to occur in submicron regions doped by implantation.