This book represents a comprehensive text devoted to charge transport at semiconductor interfaces and its consideration in device simulation by interface and boundary conditions. It contains a broad review of the physics, modelling and simulation of electron transport at interfaces in semiconductor devices. Particular emphasis is put on the consistent deriva­ tion of interface or boundary conditions for semiconductor device simula­ tion. The book is of interest with respect to a wide range of electronic engineering activities, as process design, device design, process character­ ization, research in microelectronics, or device simulator development. It is also useful for students and lecturers in courses of electronic engineering, and it supplements the library of technically oriented solid-state physicists. The deepest roots of this book date back to the mid-seventies. Being a student of electrical engineering, who was exposed for the first time to the material of semiconductor device electronics, I was puzzled by noticing that much emphasis was put on a thorough introduction and understand­ ing of the basic semiconductor equations, while the boundary conditions for these equations received very much less attention. Until today on many occasions one could get the impression that boundary conditions are unimportant accessories; they do not stand on their own besides the bulk transport equations, although it is clear that they are of course a necessary complement of these.