A model for scanned probe microscope (SPM) silicon oxidation is presented. The model was derived from a consideration of the space-charge dependence of this solid-state reaction as a function of substrate doping type/level and has been verified experimentally by integrating an in situ electrical force characterization technique, scanning Maxwell stress microscopy (SMM), into the SPM fabrication process. This system enables us to obtain SPM topographic, SMM capacitance, and SMM surface potential information of nanometer-scale oxide features as a function of ionic concentrations within the growing oxide film. SPM oxide properties are compared to those of anodic and thermal oxides. The predictive power of the resulting model is demonstrated by showing how the growth rate and electrical character of the SPM-oxide features can be altered dramatically by modulating the applied oxidation voltage.