A narrow-emitter effect in submicrometer, single-polysilicon emitter BJTs is investigated. The effect is a result of the two dimensional diffusion of the impurity atoms that are redistributed in the polysilicon during thermal cycles. This effect results in geometry scaling-dependent doping profiles in the emitter and base regions, and is more significant for submicrometer and deep-submicrometer BJTs. Electrical measurements and two-dimensional process simulations were performed to demonstrate this effect.<<ETX>>