Penetration profiles of P+ions with energy between 70 and 150 keV incident 7.5° off the ⟨100⟩ axis on silicon covered with a SiO2layer of thicknesses ranging from 0.05 to 0.20 &mgr;m were studied both experimentally and by computer simulation. Electrical measurements were routinely performed, but occasionally CAMECA ion‐probe measurements were carried out to obtain chemical profiles. For a given energy of implantation, maximum penetration occurs when the oxide thickness produces an angular spreading of the misaligned incident beam with maximum transmitted intensity along the crystallographic direction. This suggests that the tails are due to a channeling process, in agreement with the finding by Bloodetal. in bare silicon. It is also shown that diffusion occurs after 1/2‐hannealing at 900 °C, implying the presence of a high‐diffusivity region around the penetration tail.