We studied the electrical properties of polysilicon/hafnium (Hf)-silicate gate stacks with various controlled Hf/(Hf + Si) compositions, using bis-dimethylamino-silane (BDMAS: SiH2[N(CH3)(2)](2)) and tris-dimethylamino-silane (TDMAS: SiH[N(CH3)(2)](3)) as precursors. The high-k films were fabricated by atomic layer deposition (ALD) using Hf[N(CH3)(C2H5)](4) and each of the Si precursors in turn. O-3 was used as an oxidant. Effective oxide thicknesses (EOTs) were reduced in line with increasing Hf contents: the very thin dielectric (EOT = 1.18 nm) was fabricated with a Hf/(Hf + Si) composition of 74%. The flatband voltage (V-FB) shift of p-type metal oxide semiconductor field effect transistors (p-MOSFETs) employing either Si precursor were improved by reducing the Hf/(Hf + Si) composition: the value of VFB shift was improved to about 0.25-0.26 V for Hf-silicate gate stacks in which Hf/(Hf + Si) composition was reduced from 72-74% to 21-23%. The subthreshold swings (S values) were dependent on the Hf content in the p-MOSFETs employing both Si precursors. By using the gate length (Lg) of the transistors as 75 nm, S values varied from 92 to 105 mV/dec for Hf/(Hf + Si) composition ratios from 21 to 74%, respectively, due to a Fermi-level pinning problem. Inspection of subthreshold characteristics of n-MOSFETs revealed values of I-on at V-dd = 1.1 V, which were greater than 350 mu A/mu m, while I-off was less than 50 mu A/mu m, using either Si precursor (Lg = 75 nm). With the p-MOSFETs, the values of I-on at V-dd = -1.1 V for Hf-silicate gate stacks in which Hf/(Hf + Si) composition was between 21 and 23% were approximately 30-40 mu A/mu m greater than those in which Hf/(Hf + Si) composition was between 72 and 74%. The leakage current densities were dependent on the Hf content in the Hf-silicate gate stacks. However, those were independent of the Si precursors for the Hf-silicate gate stacks with the same Hf content, because the carbon impurity concentrations near the surface of the annealed layers at 1000 degrees C were about 1 x 10(20) cm(-3) for both Si precursors. (c) 2006 The Electrochemical Society.