| 摘要 |
A method of fabricating a flash memory is provided. The flash memory structure is formed with buried bit lines that are lower in resistance, are shallower in buried depth into the substrate, and have a larger punchthrough margin than the prior art. The flash memory structure is constructed on a semiconductor substrate. A tunneling oxide layer is formed over the substrate. A plurality of floating gates is formed at predefined locations over the tunneling oxide layer. A plurality of sidewall spacers is formed on the sidewalls of the floating gates. A plurality of selective polysilicon blocks is formed over the substrate, each being formed between one neighboring pair of the floating gates. An ion-implantation process is performed to dope an impurity element through these selective polysilicon blocks into the substrate to thereby form a plurality of impurity-doped regions in the substrate to serve as a plurality of buried bit line for the flash memory device. A plurality of insulating layers is formed respectively over the selective polysilicon blocks. A dielectric layer is formed to cover all of the floating gates and the insulating layers, and finally, a plurality of control gates are formed over the dielectric layer, each being located above one of the floating gates.
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