The atomic layer deposition (ALD) of aluminum films using trimethylaluminum [TMA, Al-2(CH3)(6)] and a hydrogen plasma was examined to improve the surface morphology with good step coverage. The most important role of the hydrogen plasma was to act as a reducing agent for TMA. The film properties were analyzed using field-emission scanning electron microscopy, atomic force microscopy, Rutherford backscattering spectroscopy, and elastic recoil detection-time of flight. The growth rate was saturated at similar to0.15 nm/cycle, and the thickness was proportional to the number of reaction cycles. Repeating this reaction cycle led to controlled layer-by-layer growth. The root-mean-square roughness value of a 7.5 nm thick Al film was 0.195 nm, and ALD films had excellent step coverage on high aspect ratio trenches. (C) 2002 The Electrochemical Society.