In the presence of an interfacial layer and semiconductor surface states, a Schottky barrier height &phgr;bdecreases with increasing electric fieldEat the surface of the semiconductor. If the semiconductor doping concentrationNdis uniform throughout the depletion region and if[ (qNd/&egr;) (d&phgr;b/dE)−E] [ (d2&phgr;b/dE2) (dE/dV) ]≪1,whereVis the applied voltage and &egr; is the semiconductor permittivity, the slope of the (capacitance)−2vs voltage relationship is constant and can be interpreted to giveNd. The voltage intercept of the relationship yields an apparent barrier height &phgr;arelated to the true barrier &phgr;bby &phgr;a=&phgr;b−E(d&phgr;b/dE) + (qNd/2&egr;) (d&phgr;b/dE)2, whereqis the electron charge. From the measured variation of &phgr;awithNdand one absolute measure of &phgr;bat one value ofNd, &phgr;b(E), andd&phgr;b(E)/dEmay be deduced. Fromd&phgr;b(E)/dEthe surface state density as a function of energy in the bandgap and the minimum value of interface thickness divided by relative interface permittivity can be obtained. Using the data of Archer and Atalla for vacuum cleaved Au‐Si diodes to illustrate our method, the surface state density is found to peak at a value of ∼2×1014cm−2·eV−1at about 0.83 below the conduction band and the minimum value of interface thickness divided by relative dielectric constant is found to be of the order of 5 Å. Criteria are given which show how Schottky diode capacitance‐voltage data may be further used, in conjunction with photoelectric barrier measurements, to detect the presence of deep lying impurities or the penetration of surface state charge into the body of the semiconductor.