B-doped p(+) polycrystalline-silicon (poly-Si) or silicon germanium (poly-Si0.73Ge0.27) gate/Al2O3 or top nitrogen incorporated Al2O3 (N-Al2O3)/n-type Si (100) metal insulator semiconductor capacitors were fabricated using atomic layer deposition for the Al2O3 or AlN/Al2O3 layer to investigate B penetration and device reliability. The adoption of a poly-Si0.73Ge0.27 electrode greatly reduced the B penetration into the substrate through the Al2O3 layer and enhanced the activation of the implanted dopant compared to the poly-Si electrode under a given activation annealing condition. The acquired work function engineering by the poly-Si0.73Ge0.27 electrode also reduced the threshold voltage of the device. Deposition of a thin AlN layer on top of the Al2O3 layer further reduced the B diffusion into the dielectric which greatly enhanced the dielectric reliability. The polySi(0.73)Ge(0.27)/(N-Al2O3)/n-type Si capacitors showed the smallest leakage current density of 3.0 x 10(-7) A/cm(2) at 1 V and a large charge-to-breakdown value of 8.5 C/cm(2). (c) 2006 The Electrochemical Society.