Elastoresistance ofn‐type silicon on sapphire is measured. The measurement is performed with a gated MOS Hall bridge. An extrapolation method is developed to minimize errors due to aluminum autodoping. From the obtained result, it is concluded that the lateral stress present in the silicon causes almost complete depopulation of the energy surface in thekzdirection, perpendicular to the surface of the silicon. This in turn causes pronounced changes in the transport properties, such as resistivity or Hall mobility. Qualitative agreement with the theory, in which no scattering mechanism is considered, is obtained.