A multilayer heterostructure of Si(50 nm)/Co(50 nm)/Si(50 nm)/Si⟨ 100⟩ was prepared by an e-beam evaporation technique under UHV conditions and it was then subjected to irradiation by 120 MeV Au⁺ ions with fluence varying between 10¹³ and 10¹⁴ ions cm⁻². No external thermal treatments were used. Secondary ion mass spectrometry was used in the depth profile mode, which indicated a monotonic increase in the mixing width with fluence at the first interface of Si/Co. Depth profile analysis suggested major changes in the preferential sputtering rates of Co at the interface indicating formation of silicides. Further investigation by x-ray diffraction confirmed the formation of different phases of cobalt silicides, Co₂Si, CoSi and CoSi₂, as a buried layer, while the Raman spectroscopy showed broad peaks near 325 and 725 cm⁻¹, which are characteristic of the CoSi₂ phase. The above work suggests that swift heavy ion irradiation can be advantageously used for interconnect related buried layer silicide formation at room temperature avoiding thermal annealing.