This paper analyzes the delamination phenomena for nonpatterned Cu/ultralow-K (ULK) wafers during abrasive-free chemical mechanical polishing (CMP) by finite element (FE) analysis. The objectives of this study are as follows: to find the major cause and major parameter of the CMP-induced delamination and to suggest better conditions to prevent the CMP-induced delamination. Through the FE analysis, we found that the maximum principal stress within the cap layer was the critical stress for the CMP-induced delamination. This means that the failure such as fracture of the cap layer incurs the CMP-induced delamination. Through the parametric study, we also found that the maximum principal stress within the cap layer is very sensitive to the modulus of the cap layer and the modulus of ULK.