Semiconductor fabrication process for integrating formation of embedded nonvolatile storage device with formation of multiple transistor device types

Abstract

A semiconductor fabrication process includes forming polysilicon nanocrystals on a tunnel oxide overlying a first region of a substrate. A second dielectric is deposited overlying the first region and a second region. Without providing any protective layer overlying the second dielectric in the first region, an additional thermal oxidation step is performed without oxidizing the nanocrystals. A gate electrode film is then deposited over the second dielectric and patterned to form first and second gate electrodes. The second dielectric may be an annealed, CVD oxide. The additional thermal oxidation may include forming by dry oxidation a third dielectric overlying a third region of the semiconductor substrate. The dry oxidation produces a interfacial silicon oxide underlying the second dielectric in the second region. An upper surface of a fourth region of the substrate may then be exposed and a fourth dielectric formed on the upper surface in the fourth region.