The influence of substrates on the elastic reaction of a thin film was investigated using a load- and depth-sensing microhardness tester. For the investigation silicon oxide films were produced in a radio frequency (r.f.) plasma with hexamethyldisilane and oxygen, on <111> silicon wafers and glass ribbons simultaneously for the first set of samples and on <111> silicon wafers but with various film thickness for the second set. The Young’s moduli of the silicon oxide films were measured to be different for the different substrates for the same thickness of film. The Young’s moduli of the silicon oxide films decreased for the same substrate with increasing film thickness to approach the Young’s modulus of a silicon oxide film. The elastic deformation was considered for the normal point load to a flat quasi-infinite surface using an elementary theory of elasticity under the assumption of perfect adhesion between the him and substrate. The Young’s modulus of the film was recalculated using the equation derived, considering the elastic deformation of the normal point load to a flat quasi-infinite surface. The recalculated film Young’s modulus of 67 +/- 1.5 GPa was nearly independent of the film thickness, which is comparable with the modulus value of thermally grown silicon oxide.