The emissivity of a silicon wafer during the growth of thin oxide films was studied from the viewpoint of spectral, directional, and polarization characteristics of thermal radiation. Experimental results were mostly coincident with simulated results. By using a simulation model to estimate the optical properties of silicon wafers, a direct relationship was found between the ratio of p- to s-polarized radiance and the polarized emissivity under specific conditions. This relationship was experimentally confirmed at high temperatures (>900 K). On the basis of these results, the present study proposes a new radiation thermometry technique that can measure the temperature and spectral polarized emissivity of a silicon wafer at a wavelength of 0.9 µm and at moderately high temperatures, irrespective of the variation in emissivity with oxide film thickness.