Patent ID: 6414372
Filing Date: 2002-07-02
Classification: H01L

Abstract:
A bipolar transistor fabricated on a silicon substrate of a first conductivity type, comprising:a heavily doped impurity region formed in a surface portion of said silicon substrate and having a second conductivity type opposite to said first conductivity type, a recess being formed in a surface portion of said heavily doped impurity region; a lightly doped epitaxial silicon layer of said second conductivity type formed in and filling said recess and having a flat zone substantially constant in dopant concentration in a direction of a depth of said lightly doped epitaxial silicon layer below a first surface portion thereof; a base region of said first conductivity type formed in said first surface portion of said lightly doped epitaxial silicon layer, said base region including a graft base region formed in a region in said lightly doped epitaxial silicon layer, and an intrinsic base region formed inside of said graft base region; a heavily doped collector contact region of said second conductivity type formed in a second surface portion of said lightly doped epitaxial silicon layer contiguous to said flat zone; and an emitter region of said second conductivity type formed in a surface portion of said base region.