Previously we have proposed a model of lattice defect, positively charged defect close to the M/S interface, which causes nonideality in nearly ideal Au/Si Schottky barrier. This model is elaborated in this paper. The T-o anomaly is caused by the spatial inhomogeneity of Schottky barrier height (SBH) due to the same defect, which is expressed by a Gaussian distribution with standard deviation sigma. The ideality factor it is related with sigma(2) which depends on applied voltage. Utilizing a relation between the local SBH lowering and the distance of defect from metal-induced gap state (MIGS), the defect distribution, 6 x 10(13) cm(-2) in total, is obtained to be confined close (about 10 Angstrom) to the MIGS. Changes of the distribution with applied bins indicate that the defect is an ionized donor in an equilibrium with neutral slate in a low SBH region. The defect is induced by the Au evaporation process which produces Au silicide. Si self-interstitial induced by the process has appropriate atomic and electronic properties as the defect with deep donor levels of the negative-U property.