A brief review is presented of the basic properties of ion beam mixing of layers of material on Si and Si02, and current models for the observed phenomena. Following this, some potential applications of ion beam mixing to processing of Si devices are reviewed. These applications are: (1) dispersal of impurities which would otherwise block thermal reactions, (2) formation of uniform, well-aligned metal-silicide contacts to devices, and (3) adhesion of metal interconnects to Si02 layers. In each of these, the mixing is executed with a simple implantation step, conducted at room temperature. The alternative processes are mostly either more complex, or require annealing at very high temperatures.