A simulation method includes storing a plurality of structure parameters of transistors for a semiconductor chip, imaging generating a first local layout which includes a first structure parameter extracted from a semiconductor device included in the first local layout, the first structure parameter being an actual parameter determined using the imaging equipment, generating second to n-th local layouts by modifying the first structure parameter included in the first local layout, wherein the second to n-th local layouts respectively have second to n-th structure parameters modified from the first structure parameter, calculating first to n-th effective density factors (EDF) respectively for the first to n-th structure parameters, determining a first effective open silicon density for a first chip using the first to n-th effective density factors and a layout of the first chip, and calculating first to m-th epitaxy times for first to m-th effective open silicon densities.