Crystalline In-Ga-Zn Oxide (IGZO) including c-axis aligned crystal (CAAC) enables FETs to show high reliability and extremely low off-state current. CAAC-IGZO technology is expected to grow to main technology of next-generation displays and is already contributing to mass-production of liquid crystal displays. In this paper by focusing on a very important feature of CAAC-IGZO FET, extremely low off-state current, its pioneering various applications to LSI are reviewed and discussed. In particular, a success in development of a hybrid process of CMOS FETs and CAAC-IGZO FETs promotes our developments of novel memories, processors, image sensors, and recently, field programmable gate arrays (FPGA).