Tremendous progress of the silicon integrated circuits (ICs) has been driven by the downsizing of their components such as MOS field effect transistors (MOSFETs) over 30 years. In order to maintain the progress for future, every dimension of the MOSFETs has to be shrunk continuously with almost the same ratio. However, the dimensions are now close to their limit of downscaling, and further reduction becomes very difficult. In order to solve the problem, the introduction of new materials and structures are seriously considered. High-k gate insulator technology is one of the examples being developed seriously to overcome the problems. In this paper, progress of silicon IC technologies for the past 30 years is described at first. Then, the difficulties of the further downsizing for future are explained in detail. Finally, the efforts to solve difficulties and the possible solutions are described.