Patent ID: 6150225
Filing Date: 2000-11-21
Classification: H01L

Abstract:
A method for fabricating a semiconductor device comprising:forming a first buried layer of a first conductivity type on a semiconductor substrate of a second conductivity type;forming a second buried layer of a second conductivity type on said semiconductor substrate;forming an epitaxial layer of said first conductivity type on said first buried layer, said second buried layer and said semiconductor substrate, wherein a first impurity of said first buried layer diffuses into said epitaxial layer to form an expanded first buried layer having an upper surface with a first depth from a surface of said epitaxial layer, and a second impurity of said second buried layer diffuses into said epitaxial layer to form an expanded second buried layer having an upper surface with a second depth from said surface of said epitaxial layer shallower than said first depth;forming a first diffusion layer of said second conductivity type from said surface of said epitaxial layer to said upper surface of said second buried layer, and a second diffusion layer of said second conductivity type in a first portion which is above said layer; first buriedforming a third diffusion layer of said first conductivity type from said surface of said epitaxial layer to said first buried layer; andforming a fourth diffusion layer of said second conductivity type formed in a second portion which is above said first buried layer.