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Abstract: Superjunction devices (SJDs) are a novel class of power devices which break the physical limit of silicon with respect to the area-specific turn-on-resistance. SJDs consist of a modified vertical MOSFET structure which is characterized by additional deep pillar-like p-type regions formed inside the n(−) epi-layer below the transistor gate. In the present investigation ultra-high energy boron ion implantation of 2–25MeV was applied for forming the deep p-type regions laterally structured using Si stencil masks. For energies above 12MeV the incident ions exceed the Coulomb barrier for Si which leads (i) to a significant gamma and neutron emission during implantation and, (ii) an activation of the wafer and the mask material. However, the most relevant reaction for activation (11B+ 28Si→ 39K(nα)→ 34mCl(β,EC)→ 34S) has a half-life time of only 32min, hence the radiation level of the wafers drops below the critical limit within the processing time. Based on the described technology Infineon Technologies successfully prepared a set of prototype wafers with fully functional high-voltage transistors. Typical blocking capability was approx. 560V with an area-specific turn-on-state resistance of about 3.85Ωmm2. [Copyright &y& Elsevier]