Laser-assisted atom probe tomography (LA-APT) was applied to SiN thin films with enriched N-15 isotope in order to investigate the possibility of obtaining the nitrogen distribution in silicon-based structures by LA-APT analyses. SiN films with the ratio N-14:N-15 of similar to 0:1 ((SiN)-N-15) and similar to 1:1 ((SiNN)-N-14-N-15) were formed on Si substrates, and measured by LA-APT under the usage of 355 nm-wavelength pulsed laser. The mass spectra obtained showed that the nitrogen counts were dominated by N-2(+). The peak-tops of Si-30(++) and N-15(+), as well as those of Si-30(+) and N-15(2)+, were resolved in the mass spectrum of (SiN)-N-15. It demonstrated that nitrogen distribution could be examined quantitatively as well as qualitatively. (C) 2015 Elsevier B.V. All rights reserved.