Epitaxial fully strained Si films are known to form an effective passivation of the Ge(1 0 0) surface. However, we show using low-energy secondary ion mass spectrometry (SIMS) that considerable Ge surface segregation occurs for Si films grown from SiH4 at 500 °C. In this study, we develop an alternative deposition process at 350 °C using Si3H8 which significantly decreases the Ge peak at the Si surface. We attribute this strong reduction mainly to the fact that growth at 350 °C from trisilane proceeds below the Si–H desorption temperature. Charge pumping measurements on n-type Ge devices show a reduction by approximately a factor three in the high-k/substrate interface trap density for the samples with 350 °C Si passivation, compared to those using a Si passivation deposited at 500 °C.