The concomitant downscaling and diversification of MOS device architectures for future technology nodes requires new materials to reach the expected specifications. This is especially the case for top level metal interconnections, which suffer from significant narrowing. The currently used Cu is pushed to its physical limits, being mainly restricted by a long electron mean free path (e-MFP) of ~40 nm. Ru has been identified as a promising alternative, thanks to its shorter e-MFP (< 7 nm). In this work, we report on the electrical and structural properties of laser-annealed 30 nm-thick Ru layer. Prior to the layer of interest, a 1.5 nm-thick TiN diffusion barrier was deposited by PVD on top a 100 nm-thick SiO2, grown on a Si(100) substrate. The layer stack was annealed in a SCREEN platform, equipped with a monochromatic (355 nm) high-frequency microsecond scanning pulsed laser (µs UV-LA), at room temperature and under a N2 flow. A large range of thermal budgets were applied by fixing the energy density (ED) and varying the irradiation time (IT). Electrical properties were monitored through the sheet resistance, using 4-point probe measurement while structural properties were studied by TEM/STEM (plan-view and cross-section) and XRD. The TiN diffusion barrier effectiveness was confirmed by STEM-EDX. The measured sheet resistance of the as-deposited Ru film is ~7.3 Ω/sq (corresponding to 22 µΩ.cm). For a given ED, increasing the IT allows to obtain a 53% decrease of the initial sheet resistance value (~3.5 Ω /sq, corresponding to ~10.5 µΩ.cm). According to TEM plan-view observations, the mean grain size increases from 10.2 ± 2.6 nm (as-deposited) to 70.1 ± 30.7 nm (annealed) This reduces considerably the density of grain boundaries and thus the density of scattering centers. Cross-section images confirmed that the Ru grain size distribution broadening with µs UV-LA is correlated with a structure modification, from randomly-superimposed small grains to a columnar structure, composed by individual large grains covering the whole film thickness. When the IT is further increased, two phenomena are observed: a surface morphology alteration and grain buckling. The first arises from the local melting of the underlying silicon, leading to the formation of periodic wrinkles (micrometer scale). The second phenomenon can be explained by the internal stress increase inside the Ru film, due to grain enlargement (nanometer scale). The sheet resistance evolution with the grain size follows closely the predictive models found in literature, which suggests that the electrical properties of the annealed Ru films are not significantly impacted by the mechanical stresses. Based on these results, we propose solutions that can extend the favorable process window such as: using a heating chuck during laser annealing, performing multi-pulse mode process, changing gas environment conditions, as well as optimizing the layer stack thicknesses for reflectivity engineering.