Compressively strained SiGe has been used in nanometer devices, for example, as high mobility channel [1] in MOSFET and low-bandgap source in tunnel field effect transistor to increase the tunneling probability [2] . For nanometer devices, source/drain contact resistance is becoming comparable or larger than intrinsic channel resistance [3] . Ni germanosilicide is one promising option for SiGe contacts. However, synthesis of homogeneous germanosilicide is challenging due to agglomeration and Ge segregation. Ni(Al)SiGe epitaxy growth by incorporation of Al mediation layer on a relaxed SiGe substrate has been reported [4] . In this paper we present results on the formation of very homogeneous Ni(Al)SiGe with sharp germanosilicide/SiGe interfaces on strained SiGe, which has potential for various device applications. 3 cycles of {Ni/Al} layers with different Al concentration were deposited on strained SiGe substrate and rapid thermal processing was followed to form germanosilicides. Transmission electron microscopy(TEM) results shown in Figures 1 and 2 indicate that the most uniform germanosilicide layer with a sharp interface to the SiGe layer was formed with 20% Al at 400°C. Corresponding RBS/channeling results presented in Figure 3 further confirm that the layer formed at 400°C with 20% Al shows better crystalline quality indicated by the lower channeling yields. The Al content modulates the Ni diffusion, thus resulting in different germanosilicide morphology.The Al mediation effect is temperature dependent, as shown in TEM results (Figure 2) for samples with 20% Al. Higher Ni diffusivity at higher temperature is attributed to be the main reason. The competition between Ni diffusivity and Al barrier effect leads to different stoichiometry (Figure 4). Al mediation effect can also be seen intuitively in secondary ion mass spectrometry (SIMS) results of samples formed with 10% and 20% Al at 400 ºC (Figure 4): Ni and Al distribute homogeneously in germanosilicide layer while it is different for the sample with 10% Al. With high resolution TEM and the electron diffraction pattern (Figure 5) the germanosilicide phase formed at 400°C with 20% Al is identified as B8 type Ni 5 (SiGe) 3 . References: [1]