Patent ID: 7288829

Claim:
A bipolar transistor comprising: a substrate; a collector in said substrate; an intrinsic base above said collector; an extrinsic base adjacent to said intrinsic base, wherein, on at least one side of said intrinsic base, said extrinsic base comprises multiple extrinsic base implant regions comprising at least: a first implant region adjacent to said intrinsic base and having a first depth; and a second implant region adjacent to said first implant region and having a second depth that is greater than said first depth; an emitter comprising: a lower portion above said intrinsic base and having a first sidewall; and an upper portion above said lower portion and having a second sidewall, wherein said upper portion is wider than said lower portion such that a section of said upper portion extends laterally beyond said first sidewall and wherein said first implant region is aligned below said section from said first sidewall of said lower portion to said second sidewall of said upper portion; and a sidewall spacer adjacent to said second sidewall, wherein said sidewall spacer is above said second implant region and wherein a step from said first depth of said first implant region to said second depth of said second implant region is aligned with said second sidewall.