Embodiments herein describe techniques for a semiconductor device including a Ge substrate. A passivation layer may be formed above the Ge substrate, where the passivation layer may include one or more molecular monolayers with atoms of one or more group 15 elements or group 16 elements. In addition, a low-k interlayer may be above the passivation layer, and a high-k interlayer may be above the low-k interlayer. Furthermore, a metal contact may be above the high-k interlayer. Other embodiments may be described and/or claimed.