Method of forming an embedded memory

Abstract

A method of forming an embedded memory integrating nitride read only memory starts by forming an ONO layer and a protective cap layer on a surface of a semiconductor substrate defined with a memory area and a periphery area. The periphery area has a first, a second and a third device area. An etching and a first ion implantation process form each bit line in the memory area. A spacer is then formed at either side of the protective cap layer and the ONO layer in the memory area, and the protective cap layer and the ONO layer are removed in the first device area. The threshold voltage for the first device area is adjusted and a first thermal oxidation process forms a buried drain oxide layer atop each bit line and a first gate oxide layer on the surface of the first device area, respectively. The protective cap layer and the ONO layer are removed from the second device area and the third device area, and a second gate oxide layer is formed in the second device area and the third device area. Finally, the protective cap layer in the memory area and the second gate oxide layer in the third device area are removed, and a third gate oxide layer is formed in the third device area.