Device structures and technologies for high-speed logic CMOS LSIs have been reviewed, covering the range from several microns to the far future of 1/40 micron devices. The future 0.25 to 0.1 pm generation was investigated in detail. In this generation, optimum design of the impurity profile and fine control over impurity doping - to suppress short-channel effects and to minimize the series source/drain resistance will be die critical issues. New doping techniques will need to be developed to meet the requirements. Intelligent CAD systems which are able to create an optimum interconnect design for high-speed operation will become indispensable, as will highly reliable circuits. For the sub-tenth micron range, undoped epitaxial channel MOSFETs and double-gate SOI MOSFETs appear to be most promising, and correct operation of these devices was confirmed through simulations. However, no concept of a realistic ULSI based on these transistors is available at this point.