Patent ID: 7781295

Claim:
A method for manufacturing a bipolar junction transistor, said method comprising the steps of: forming a shallow trench isolation structure in a collector structure, the shallow trench isolation structure surrounding a base active area and a collector contact area; forming a window stack material over the collector structure, the window stack material covering the collector contact area and first portions of the shallow trench isolation structure, the window stack material not covering the base active area and second portions of the shallow trench isolation structure; forming a first base layer over the base active area and the window stack material, the first base layer comprising silicon material mixed with an impurity material; forming a second base layer that comprises substantially only silicon material over said first base layer; forming an emitter layer over said second base layer, said emitter layer comprising substantially only silicon material; placing a resist mask over a portion of said emitter layer; applying an etch procedure to etch exposed portions of said emitter layer to form an emitter under said resist mask; and continuing to apply said etch procedure to etch exposed portions of said second base layer down to said first base layer.