In this work,an in-situ ozone treatment is carried out to improve the interface thermal stability of HfO2/Al2O3 gate stack on germanium (Ge) substrate.The micrometer scale level of HfO2/Al2O3 gate stack on Ge is studied using conductive atomic force microscopy (AFM) with a conductive tip.The initial results indicate that comparing with a non insitu ozone treated sample,the interface thermal stability of the sample with an in-situ ozone treatment can be substantially improved after annealing.As a result,void-free surface,low conductive spots,low leakage current density,and relative high breakdown voltage high-κ/Ge are obtained.A detailed analysis is performed to confirm the origins of the changes.All results indicate that in-situ ozone treatment is a promising method to improve the interface properties of Ge-based three-dimensional (3D) devices in future technology nodes.