Ge-MIS structures have attracted attention as next-generation CMOS devices. We have reported that a GeNx/Ge structure with a low interface state density can be made by the electron cyclotron resonance (ECR) plasma technique, and that the interface state density of Ge-MIS structures can be evaluated through characteristic analysis in the inversion region even at room temperature. In this report, we evaluate the interface state density of p-type and n-type GeNx/Ge structures using the conductance technique at low temperature and characteristic analysis at room temperature, and the related process dependences. We have successfully evaluated the interface characteristics of GeNx/Ge structures. The interface state density was systematically distributed with respect to the midgap, and the density near the midgap was close to that of the GeO2/Ge structure. (C) 2015 Wiley Periodicals, Inc.