| 摘要 |
A method is described which forms an MOS transistor having a narrow diffusion region that is smaller than the diffusion region defined using photoresist in a conventional CMOS processing. In one embodiment, LOCOS can be used to form isolation (e.g., shallow trench) between active devices. A polysilicon layer is then deposited and doped either n+ or p+ selectively. The polysilicon layer is then patterned. Next, a dielectric layer and a refractory layer are deposited over he patterned polysilicon layer. Next, a contact hole with a high aspect ratio is defined in the oxide where the transistor will be formed. Angled implant of lightly-doped drain (LDD) regions or graft source/drain regions are formed on two opposite sides of the contact hole. The refractory metal layer is then removed. Spacers are then formed on opposite sidewall of the contact hole. A gate oxide layer is either thermally grown or deposited in the contact, before or after spacer formation. A gate material is then deposited into the contact hole to form a gate electrode. The gate electrode and the dielectric layer are polished to become coplanar.
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