| 摘要 |
A buried bitline (BB) may be formed in at least two separate implantation steps, in addition to a pocket implant step. The pocket implant has a first width (W 1 ) and a first depth (D 1 ); the first BB implant has a second width (W 2 ) defined by first sidewall spacers and a second depth (D 2 ); the third BB implant has a third width (W 3 ) defined by second sidewall spacers and a third depth (D 3 ); the second width (W 2 ) is less than the first width (W 1 ), and the third width (W 3 ) is less than or equal to the second width (W 2 ); and the second depth (D 2 ) is greater than the first depth (D 1 ), and the third depth (D 3 ) is greater than the second depth (D 2 ). The first BB implant may provide for pocket implant (PI) to bitline (BL) edge optimization; and the second BB implant may provide for controlling BL resistance.
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