Advances in power semiconductor devices are discussed, focusing on the adaptation of silicon integrated circuit wafer processing methods to the design and fabrication of power devices. Some basic properties of power devices are reviewed, along with recent adaptations of wafer processing technology. Two trends are discerned: increasing use of self-aligned, double diffused MOS gate structures to achieve devices with low-current drive requirements; and movement toward an ideal one-dimensional device, thereby making more efficient use of the available area. Different devices are compared. Techniques that have potential for use in power device are discussed: use of trenches, direct wafer bonding, cellular bipolar transistors, and junction termination. The combination of power switches with control logic on the same chip is briefly considered. >