The oxygen content in zone melting recrystallization silicon‐on‐insulator (ZMR SOI) layers with thicknesses ranging between 0.5 and 25 &mgr;m obtained with a movable lampheater is studied. Secondary‐ion‐mass spectrometry profiling as well as numerical calculations are presented. The simulations are based on oxygen redistribution during cooling down. In the model it is assumed that the interface reaction is fast enough to be not the rate‐limiting step in the redistribution process. Consequently, the oxygen transport was considered to be entirely diffusion limited. Good agreement was found between the measurements and calculated values. The profiles show a maximum at the center of the layer and symmetrically depleted regions in the top and bottom of the silicon film. It has been generally accepted that ZMR SOI layers have a high oxygen concentration corresponding to the saturation level at melting point. In the present study, however, we show that in the 0.5‐&mgr;m layers the oxygen concentration is as low as 1×1017(O atoms)/cm3.