Boron diffusion from B-doped polycrystalline silicon through Hf silicate gate dielectric films into Si substrate was investigated. The dopant penetrated into the Si substrate as a result of high-temperature processing. This dopant penetration is a significant problem because it induces a gate threshold voltage shift. Therefore, backside-SIMS was applied to investigate the dopant diffusion profile in thin Hf silicate films. Backside-SIMS makes it possible to measure the dopant profile in Hf silicate films accurately without remnant surface species and atomic mixing effects from the high-doped poly-Si gate electrode. Using backside-SIMS analysis, it was confirmed experimentally that the introduction of N into Hf silicate films is effective for suppressing dopant diffusion. (C) 2004 Elsevier B.V. All rights reserved.