In this work, we have correlated the electrical characteristics of ultrathin oxide with the presence of pinholes by C-AFM studies. Ultrathin gate oxide has been grown thermally as well as by chemical treatment with HNO3, followed by selective anodic oxidation. The results of C-AFM studies confirm that the improvement in the gate leakage current in thermally grown oxide is indeed due to the filling of pinholes by selective anodic oxidation, while the absence of pinholes in the chemically grown oxide explains why there is no improvement in the gate leakage current after selective anodisation. (c) 2005 Elsevier B.V. All rights reserved.