Plasma is used a lot for microelectronics (and materials science) applications. About half of the many steps needed for microchip fabrication are based on plasma technology, like surface etching, coating deposition, etc. Furthermore, plasma is also extensively used for surface treatment and deposition of a large variety of coatings, and for the growth of nanomaterials, such as carbon nanotubes and graphene. In recent years, our research here mainly focuses on the microelectronics applications, for which we use a hybrid Monte Carlo – fluid model to describe the plasma chemistry and plasma-surface interactions in plasma reactors used for etching and film deposition. In addition, we use Monte Carlo feature profile simulations for modelling the formation and shape of etch trenches.