主权项 |
1. A method for fabricating a semiconductor memory, comprising:
providing a semiconductor substrate having a memory array region and a peripheral circuit region thereon; forming active areas in the semiconductor substrate; forming an oxide layer on the active areas, wherein the oxide layer acts as a gate oxide layer in the peripheral circuit region; subjecting the oxide layer to a surface treatment; depositing a first polysilicon layer, a buffer layer, and a hard mask on the oxide layer; fabricating recessed access devices in the memory array region, comprising:
forming an opening in the hard mask within the memory array region by using lithographic and etching processes, performing a dry etching process to etch the buffer layer, the first polysilicon layer, the oxide layer, and the semiconductor substrate through the opening to thereby form a trench; forming a gate oxide layer on a surface of the trench; depositing metal into the trench; and filling the trench with a dielectric layer;removing the hard mask and the buffer layer; andfabricating transistors in the peripheral circuit region, comprising:depositing a second polysilicon layer on the first polysilicon layer; andpatterning the first and second polysilicon layers into a gate structure. |