We evaluated the segregation coefficient m of B, P, and As at the polycrystalline Si/HfO2 interface. The m values of B, P, and As are between 0.3 and 1 and are similar to that of B at the polycrystalline Si/SiO2 interface. The m value of P at the polycrystalline Si/ SiO2 interface is around 1000, and this high value largely keeps P from penetrating the thin gate SiO2. Therefore, the penetration of B, P and As through a poly-Si/HfO2 layer is expected to be significant since the diffusion coefficients of P and As in HfO2 are also high, making the use of a cover layer indispensable for p(+) and n(+) polycrystalline silicon gate devices. (C) 2004 Elsevier Ltd. All rights reserved.