Method for fabricating a semiconductor device with bipolar transistor

A method of forming a bipolar transistor, comprising the steps of:

• forming a buried layer having a first conductivity type in a first single crystal silicon substrate of a second conductivity type;
• growing a second single crystal layer on said first single crystal covering said buried layer;
• forming three spaced oxidation resistance patterns on said second single crystal layer;
• forming four space-formation insulator layers between each of said spaced oxidation resistance patterns, each of said space-formation insulator layers having laterally protruding ends having a cross-sectional shape comprising a bird's beak beneath ends of said space-formation insulator layers;
• forming a collector under a third of said spaced oxidation resistance patterns between two of said space-formation insulator layers;
• forming a base electrode over a first, second, and third of said four space-formation insulator layers;
• etching an emitter contact hole through said base electrode removing said second space-formation insulator layer;
• forming an intrinsic base region and an emitter region at a bottom of said emitter contact hole;
• and
• growing a polysilicon layer in said contact hole, wherein said polysilicon layer has a cross-section comprising a bird beak shape and provides an electrical connection between said base electrode and said intrinsic base region.