Thickness uniformity of ultrathin (30–100 Å) dielectric films grown on 4 in. silicon wafers in pure N2O ambient using a specially designed rapid thermal process reactor is studied. Excellent thickness uniformity in terms of percentage standard deviation (≤5%) is observed. Metal‐oxide‐semiconductor capacitors with these thin (∼100 Å) dielectrics have been fabricated. Results show that N2O oxides exhibit comparable interface state density and slightly larger breakdown field, but significantly reduced interface state generation and charge trapping under constant current stressing compared to oxides grown in pure O2.