The beam technology developed for neutral beam injection in thermonuclear fusion research has been applied to industry. Currently, positive ion beams are widely applied to processing of semiconductors. For example, intense argon ion beams are used for milling substrates of silicon wafers, and large-area liquid crystal displays are also manufactured by implanting P+ or B+ ions on glass plates. Recently, intense negative ion beams have also been developed and are being applied to new fields in the semiconductor industry. Japan Atomic Energy Research Institute (JAERI) is developing a new technology to slice thin single-crystal semiconductor films of several tens of micrometers in thickness from the ingot without waste by implanting the MeV-class H- ion beam developed for ITER. This process is realized only by utilizing the high-energy negative ion beam since positive ion implantation requires mass separation that practically limits the ion beam energy, namely, the penetration depth of the ions. By implanting 725 keV H- ions directly onto the Si ingot, single-crystal Si plates of 10 µm in thickness have been successfully sliced. It is expected that this technology will allow the mass productions of high efficiency solar cells and micro-machines.