Spatial fluctuations of lattice strain in an as‐grown Czochralski‐grown silicon wafer, in which a ring‐shaped region of densely distributed oxidation‐induced stacking faults appears after oxidation thermal treatment, are measured by double‐crystal reflection topography with synchrotron radiation. The measured lattice strain is isolated into local variations in lattice dilation and inclination angle from an average plane. The variation profile of the lattice spacing shows a small valley in the ring‐shaped region, while showing a peak just outside the ring‐shaped region. The relation between the lattice strain and anomalous oxygen precipitation is discussed. ©1995 American Institute of Physics.