Control of dopant diffusion from polysilicon emitters in bipolar integrated circuits

An integrated circuit and a method of fabricating the same are disclosed. Complementary bipolar transistors ( 20 p , 20 n ) are fabricated as vertical bipolar transistors. The emitter polysilicon ( 35 ), which is in contact with the underlying single-crystal base material, is doped with a dopant for the appropriate device conductivity type, and also with a diffusion retardant, such as elemental carbon, SiGeC, nitrogen, and the like. The diffusion retardant prevents the dopant from diffusing too fast from the emitter polysilicon ( 35 ). Device matching and balance is facilitated, especially for complementary technologies.