| 摘要 |
An MOS device includes a gate stack overlying a semiconductor substrate and a graded source/drain region adjacent to the gate stack. The graded source/drain region includes a first grade having a first depth, a second grade spaced further apart from a channel region than the first grade, and a third grade spaced further apart from the channel region than the second grade. The depth of the second grade is between the respective depths of the first and the third grades. The MOS device further includes a silicide region on a top surface of the source/drain region wherein the silicide region has an inner edge substantially aligned with an inner edge of the third grade, and a graded gate spacer comprising an inner portion on a sidewall of the gate stack and an outer portion on a sidewall of the inner portion.
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