Deep level transient spectroscopy was applied to study silicon epitaxial layers of varying thickness grown on silicon‐on‐insulator substrates formed by oxygen implantation. For 3‐&mgr;m‐thick layers no traps were detected. For 1.0‐, 2.0‐, and 2.5‐&mgr;m‐thick layers electron traps were found with levels 0.34, 0.32, and 0.37 eV below the conduction‐band edge, and corresponding capture cross sections of ∼2.0×10−7, 6.0×10−18, and 5.0×10−7cm2. These levels were found to be uniformly distributed across the wafer. It was also observed that the trap concentration is a decreasing function of epilayer thickness.