We investigated the reaction stability of titanium, cobalt and their bilayer films with side-wall spacer materials of SiO$_2$ for the salicide process. We prepared Ti 350 $AA$, Co 150 $AA$, Co 150 $AA$/Ti 100 $AA$ and Ti 100 $AA$/Co 150 $AA$ films on 1000 $AA$-thick thermally grown SiO$_2$ substrates, respectively. Then the samples were rapid thermal annealed at the temperatures of $500^{circ}C$, $600^{circ}C$, and $700^{circ}C$ for 20 seconds. We characterized the sheet resistance of the metallic layers with a four-point probe, surface roughness with scanning probe microscope, residual phases with an Auger depth profilometer, phase identification with a X-ray diffractometer, and cross-sectional microstructure evolution with a transmission electron microscope, respectively. We report that Ti reacted with silicon dioxide spacers above $700^{circ}C$, Co agglomerated at $600^{circ}C$, and Co/Ti, Ti/Co formed CoTi compound requiring a special wet process.