Method for fabricating dual gate dielectric layers

Abstract

A method for fabricating dual gate dielectric layers on a semiconductor substrate involves utilizing a single photolithographic step to form layer stacks having two different gate dielectric layers and associated polysilicon layers, and then utilizing a physical planarization process to remove excess polysilicon and silicon oxide. According to the method, a first gate dielectric is formed on the first and second device areas of a substrate. A first polysilicon layer is deposited onto the first gate dielectric, and portions of the first polysilicon layer are removed utilizing a photolithographic process. The first gate dielectric is removed over the second device area, and a second, thinner gate dielectric is formed over the second device area. A second polysilicon layer is formed over the second gate dielectric and over the first polysilicon layer. The second polysilicon layer is then removed utilizing chemical mechanical polishing in order to form a common plane between the first polysilicon layer and the second polysilicon layer.