The possibility and suitability of micro-Raman spectroscopy as a noncontact, in-line measurement technique for boron (B) concentration in ultrathin (20~35 nm thick) Si1–xGex layers epitaxially grown on 300 mm diameter p−-Si(100) wafers, by ultrahigh vacuum chemical vapor deposition, was investigated. Raman spectra from Si1–xGex/Si(100) wafers were measured under 363.8, 457.9, 488.0, and 514.5 nm excitation. Strong correlation was found between B content and characteristics of the Si–Si Raman peak from the Si1–xGex films. As B concentration increased from undoped to 9.1 × 1020 atoms/cm3, the Si–Si Raman peak broadened and the peak height became smaller for a given Ge content. The B concentration in Si1–xGex film estimated from Raman measurement was in good agreement with secondary ion mass spectroscopy analysis results. Boron concentration as low as 8.7 × 1017 atoms/cm3 can be detected by Raman spectroscopy, which is ~30 times more sensitive than the detection limit (2.7 × 1019 atoms/cm3) of high-resolution x-ray diffraction.