A bipolar device is integrated in an active layer, wherein delimitation trenches surround respective active areas housing bipolar transistors of complementary types. Each active area accommodates a buried layer; a well region extending on top of the buried layer; a top sinker region extending between the surface of the device and the well region; a buried collector region extending on top of the well region and laterally with respect to the top sinker region; a base region, extending on top of the buried collector region laterally with respect to the top sinker region; and an emitter region extending inside the base region. The homologous regions of the complementary transistors have a similar doping level, being obtained by ion-implantation of epitaxial layers wherein the concentration of dopant added during the growth is very low, possibly zero.