A fast statistical soft-error-rate (SER) analysis approach that is nearly as accurate as computationally complex Monte Carlo SPICE simulation is discussed. These SERs had different levels of charges when collected onto a sample circuit with different latching-window sizes. The line with square symbols and the line with circle symbols represent the SERs induced by four-level and full-spectrum charge collection, respectively. As the latching-window size was set to 100 ps, the SERs obtained from four-level and full-spectrum analyses were the same. However, as the latching window size grew to 150 ps, the effective range of charge collection for SSER analysis increased from 35 to 132 fC. For the analysis using four-level deposited charges, only four transient-fault (TF) distributions were generated and could contribute to the final soft error rate.