The formation of ultrashallow junction and ultrathin active layer is demanded for intergrated circuit development to satisfy the requirements of high speed and high densrty of device.Low-energy ion implantation is very effective in this usage.This paper presents the fabrication of silicon ultrashallow junction and GaAs ultrathin active layer with thickness no more than 0.1μm by lowenergy implantation as well as the results of their applications in some devices.