This chapter provides an overview on major developments in electronics that took place and finally led to the current status of semiconductor electronics. The operation of electronic circuits relies on devices with the ability to either amplify signals or to switch between the on-state and the off-state. The critical issues include problems at the device level related to device physics, problems occurring at the chip level, and economic problems. The chapter deals with some additional critical issues affecting the operation of ultimately scaled MOSFETs and of complex integrated circuits. It discusses the prospects for “Beyond-Scaling” and “Post- complementary MOS (CMOS)” electronics. Silicon (Si) CMOS constitutes the backbone of modern semiconductor electronics. Therefore, semiconductor industry will adhere to CMOS and continue CMOS scaling as long as possible, and any new technology will be compared to Si CMOS regarding performace and cost. Obviously there a several device options considered as candidates for a possible beyond-CMOS mainstream technology.