BC high-/spl kappa//metal gate Ge/C alloy pMOSFETs fabricated directly on Si (100) substrates

Buried-channel (BC) high-/spl kappa//metal gate pMOSFETs were fabricated on Ge/sub 1-x/C/sub x/ layers for the first time. Ge/sub 1-x/C/sub x/ was grown directly on Si (100) by ultrahigh-vacuum chemical vapor deposition using methylgermane (CH₃GeH₃) and germane (GeH₄) precursors at 450/spl deg/C and 5 mtorr. High-quality films were achieved with a very low root-mean-square roughness of 3 /spl Aring/ measured by atomic force microscopy. The carbon (C) content in the Ge/sub 1-x/C/sub x/ layer was approximately 1 at.% as measured by secondary ion mass spectrometry. Ge/sub 1-x/C/sub x/ BC pMOSFETs with an effective oxide thickness of 1.9 nm and a gate length of 10 μm exhibited high saturation drain current of 10.8 μA/μm for a gate voltage overdrive of -1.0 V. Compared to Si control devices, the BC pMOSFETs showed 2× enhancement in the saturation drain current and 1.6× enhancement in the transconductance. The I/sub on//I/sub off/ ratio was greater than 5×10⁴. The improved drain current represented an effective hole mobility enhancement of 1.5× over the universal mobility curve for Si.