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We report the fabrication of heterostructure Si/sub 1-x-y/Ge/sub x/C/sub y/ channel p-MOSFETs with low-carbon Si/sub 1-x-y/Ge/sub x/C/sub y/ channels. The use of low carbon mole fraction (y=0.002) has only a small effect (/spl Lt/kT) on the valence band offset. A carbon mole fraction of this value improves the thermal stability of the channel region and makes it possible to use conventional thermal oxidation and ion implant annealing without causing layer relaxation. A peak room-temperature hole mobility of 200 cm/sup 2//Vs was measured in a device with a 30-nm channel and a germanium mole fraction ramped from 10% to 40%.