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AssigneeUnited Microelectronics Corp.
InventorsShing-Ren Shen, Kuan-Cheng Su, Chen-Hui Chung
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The invention describes recessed source/drain regions formed in trenches in the substrate that provide a smooth surface topology, smaller devils and improved device performance. The recessed source/drain regions have two conductive regions: the first upper lightly doped region on the trench sidewalls, and the second lower region under the trench bottom. In addition, two buried layers are formed between adjacent source/drain regions: a threshold voltage layer near the substrate surface and an anti-punchthrough layer formed at approximately the same depth as the lower source/drain regions on the trench bottoms. The upper lightly doped source/drain region and the anti-punchthrough layer have the effect of increasing the punchthrough voltage without increasing the threshold voltage. The upper and lower source/drain regions lower the overall resistivity of the source/drain allowing use of smaller line pitches and therefore smaller devils. Overall, the recessed source/drain regions and the two buried layers allow the formation of smaller devices with improved performance.
An improved field effect transistor device having recessed lower source and drain regions, and lightly doped upper source and drain regions, in a semiconductor substrate comprising:
Dependencies are inferred from the claim text.