We report on the experimental determination of the biaxial stress characteristic of the strain state present in strained silicon nano-stripes on insulator structures. Conventional confocal backscattering Raman spectroscopy being insensitive to the tensorial nature of strain, a methodology based on the use of polarized oblique incidence backscattering Raman spectroscopy is employed. The stress component values thus obtained are compared with those provided by grazing incidence x-ray diffraction as a reference technique. By combining the oblique backscattering configuration with polarization control of the incident and scattered beams, an efficient method for the accurate measurement of biaxial stress in patterned silicon structures results.