Patent ID: 7273776
Filing Date: 2007-09-25
Classification: H01L

Abstract:
1. A method of forming a P-well region for a PNP bi-polar transistor, comprising: performing a first ion implantation process to form a first p-doped region in a portion of an active layer of a substrate to form a portion of a buried layer for the PNP transistor; forming a first layer of epitaxial material above said active layer; forming a second p-doped region in said first layer of epitaxial material; after forming said second p-doped region, forming a second layer of epitaxial material above said first layer of epitaxial material; after forming said second layer of epitaxial material, forming a third p-doped region in said second layer of epitaxial material; and after forming said third p-doped region, performing at least one heat treating process to cause said second and third p-doped regions to migrate toward one another and thereby define a portion of said P-well, wherein said at least one heat process is performed until said second and third p-doped regions engage one another and said second p-doped region engages said first p-doped region.