| 摘要 |
<p>A structure includes an isolation ring at a top surface of a substrate. A well region of a first conductivity type is in a surface portion of the substrate. The well region includes a first portion having a top portion encircled by the isolation ring, and a second portion having a top portion encircling the isolation ring. A base resistance tuning ring includes a portion overlapped by the isolation ring, wherein the base resistance tuning ring is between the first portion and the second portion of the well region. The base resistance tuning ring is selected from the group consisting essentially of a ring of the first conductivity type, a substantially neutral ring, and a ring of a second conductivity type opposite the first conductivity type.</p> |
