Solid-phase reaction, Schottky barrier heights and contact resistivities at the interface ofTi/Si0.8Ge0.2/Si(100)systems have been investigated. At annealing temperatures below 300 °C, Ti atoms preferentially react with Si atoms. Ge atoms start to react with Ti above 400 °C andC54–Ti(Si1−yGey)2with a fraction ofy=0.12is formed by annealing at 650 °C. The annealing behavior of Schottky barrier heights suggests that the Ge composition of SiGe layers at the interface is Si-rich, which is consistent with the results on the interfacial reaction. For bothn- andp-SiGe, the Schottky barrier heights lower than those of Ti/Si(100) are obtained at 650 °C, which is considered to be related to the reaction product such asC54–Ti(Si1−yGey)2.The contact resistivities smaller than those expected from the Schottky barrier heights are obtained forp+-SiGe at 580 °C. The sheet resistance ofTi/Si0.8Ge0.2/Si(100)and Ti/Ge(100) systems decreases at annealing temperatures above 550 °C and the values are as small as that ofC54–TiSi2.