In the through Silicon via (TSV) process as a key technology for the 3-dimensional LSI, particularly in the ‘via-last process', SiNx films of high density are strongly required to prepare at low deposition temperatures. It, however, is generally known that the SiNx film prepared at low temperatures shows low film density, resulting in poor insulating barrier properties. As a solution of this issue, we propose the use of the SiNx films deposited by reactive sputtering. We can obtain the sputtered SiNx films of high density (2.78∼2.99 g/cm3) in spite of the deposition without substrate heating. The 20-nm-thick SiNx films succeed the experimental check on the barrier properties against Cu diffusion upon annealing at 700°C for 1 h. The films also show good step-coverage for a TSV with an aspect ratio of 1.5. The SiNx films prepared by reactive sputtering are a candidate for a good insulating barrier applicable to the via-last TSV process.