| 摘要 |
PURPOSE:To form a thin diffusion layer into a trench, and to improve reliability by irradiating the side wall of the trench with light ions to shape a light-ion diffusion layer and irradiating the bottom with heavy ions to form a heavy-ion diffusion layer. CONSTITUTION:Light ion beams 2 having the small mass number such as phosphorus are injected to the side wall of a trench 1a shaped to an silicon substrate 1. Repulsion is inhibited by acceleration energy higher than Thomas-Fermi- energy, and said light ion beams 2 are injected efficiently. The depth of a diffusion layer is adjusted so as to be brought to the same extent as the depth of a diffusion layer by said phosphorus, and ions are implanted. When heavy ion beams 4 having the large mass number such as arsenic are used at that time, a heavy ion diffusion layer 5 can be shaped without lowering acceleration energy. Accordingly, light ions are implanted to the side wall of the trench 1a, heavy ions are implanted to the bottom, and ions are implanted in response to each section, thus forming the uniform thin diffusion layer in the trench 1a.
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