An equivalent modeling technique for estimating the deformation of extreme ultraviolet lithography (EUVL) masks caused by a complex pattern layout has been developed. An equivalent layout pattern (ELP) model provides a means of investigating ways of improving pattern placement accuracy. The simulation model is based on the finite difference method. In order to investigate the possibility of making EUVL masks with a high pattern placement accuracy, the ELP model was used to simulate how pattern density and substrate thickness affect placement error. The results obtained agree well with those for an exact model, with the relative error being at most 4%. They suggest that, when the stresses of the multilayer and absorber films cannot be reduced, it may be useful to increase the substrate thickness to improve the pattern placement accuracy. In addition, when the exposure field covers two chips, the placement error should be reduced through proper control of the stress of the absorber film rather than by changing the absorber coverage.