Effects of electro-less Ni layer as barrier/seed layers were evaluated for high reliable and low cost Cu TSVs. To electrically characterize the effectiveness of a Ni layer as barrier/seed layers for TSV application, we fabricated the trench MOS capacitor with 5μm dia. and 50μm depth TSV array. Via holes were successfully filled by Cu electroplating by using Ni seed layer. To characterize the blocking property of the Ni layer to Cu diffusion, Cu atoms were intentionally diffused from Cu TSV by annealing at 300°C and 400°C. X-ray spectrometer (EDX) and C-t analysis results shows that Cu atoms not diffuse into t h e Si substrate via the Ni layer even after annealing at 400°C. The Ni barrier layer has good blocking properties compared to a PVD barrier layer.