dWe present a comparative study of ultra-thin SiO2 oxides grown by rapid thermal oxidation (RTO) at 800 degreesC and by standard furnace oxidation at 700 degreesC on (1 0 0) P-type silicon substrates, The SiO2 oxide thickness from 1.2 to 3.5 nm was studied, The grown SiO2 oxides present a good wafer uniformity (+/-3%) and an excellent smoothness within 2 a range according to atomic force microscopy (AFM) and scanning tunnelling microscopy (STM) analysis. Infrared spectroscopy (IR) shows a weak sub-stoichiometry of the RTO 1.2 and 2 nm SiO2 films compared to a wet 3.5 nm SiO2 oxide grown in a standard furnace. The I(V) characteristics of N+ gate capacitors are in accordance with those reported in the literature. We also show a CMOS integration of the RTO 1.2 nm oxide in a NMOSFET transistor with a gate length of 20 nm.