Physical defects have always played an important role in integrated circuit (IC) yields, and the design sensitivity to these physical elements has continued to increase in today's nanometer technologies. The modeling of defect outlines that exhibit a great variety of defect shapes is usually modeled as a circle, which causes the errors of critical area estimation. Since the outlines of 70% defects approximate to elliptical shapes, a novel yield model associated with elliptical outlines of defects is presented. This model is more general than the circular defects model as the latter is only an instance of the proposed model. Comparisons of the new and circular models in the experiment show that the new model can predict yield caused by real defects more accurately than what the circular model does, which is of significance for the prediction and improvement of the yield.