Thermal stability of AlSiCu/W/n(+)p diodes with two different W contact structures prepared by selective W chemical vapour deposition (W-CVD), was first investigated. The diodes with the self-aligned W-contacted structure were able to sustain a 30 min furnace annealing up to 500 degrees C without degradation of electrical characteristics. The diodes with the contact-hole W-contacted structure were thermally less stable than the diodes with the self-aligned W-contacted structure, presumably because the sidewall of the W-filled contact hole provided a path for diffusion of Al into the Si substrate, leading to junction spiking. The insertion of a 400 Angstrom TiN barrier layer between the AlSiCu and W films blocked the Al diffusion path; thus, the AlSiCu/TiN/W/n(+)p diode was able to retain its integrity up to 550 degrees C furnace annealing.