The continuing miniaturization of traditional semiconductor devices deep into the nano-realm and novel concepts such as molecular devices require an unprecedented attention to the detailed geometry and electronic properties on the atomic scale. This talk will examine the role of atomistic modeling – mostly on the basis of quantum mechanical ab-initio methods – for current and future semiconductor process and device simulations. First, we will discuss atomistic enhancements of traditional process modeling to include nano-scale effects and the nanoscale characterization problem for conventional devices, where traditional characterization techniques cannot provide the needed information anymore. We discuss a coupled experimental-theoretical approach based on analytical transmission electron microscopy techniques (Z-contrast spectroscopy and electron energy-loss spectroscopy) that can detect single dopant atoms and even allow to “see” the atomic structure of amorphous oxide layers. With this method, we could identify for the first time an “ideal” interface between Si:Ge and SiO2. Secondly, we will discuss simultaneous process and electron-transport modeling on the atomic scale for the example of a carbon nanotube Schottky device with titanium leads. Whereas several groups have suggested ways to study electron transport through molecular devices, few concepts exist to date how to determine sensible finite-temperature contact structures between molecule and the contacting metal. We propose using ab-initio accelerated dynamics methods to study contact evolution and examine the considerable influence of the contact structure on the electron transport. We will show that electronegativities and phase diagrams can be used as predictors for contact formation.