The Cu contamination behavior of 3D integrated circuits under thermal and electric field stress was studied by monitoring the degradation of the pn(+) diodes performances of the nMOSFETs. For Cu/SiO2/Si-devices, the leakage current of the pn(+) diodes increased after thermal stressing, which indicates using SiO2 as an insulation layer is quite dangerous for Cu contamination. With the nMOSFET was turned-on, only the leakage current of the bulk-source diode increased, which suggested that the Cu contamination occur preferentially to the source than drain region. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.018205esl] All rights reserved.