The invention relates to a bipolar transistor and a method for producing same. The aim of the invention is to provide a bipolar transistor and a method for producing same, which during the use of a single-process poly-silicon technology with differential epitaxis for the production of bases overcomes the disadvantages of conventional systems, so as notably further to improve the high-speed properties of a bipolar transistor, provide highly conductive connections between the metal contacts and the active (internal) transistor region and a minimized passive transistor surface while at the same time avoiding greater process complexity and increased contact resistances. To this end, by creating suitable epitaxis conditions a poly-silicon layer is deposited on the insulating area which is thicker than the epitaxis layer in the active transistor area. The greater thickness of the poly-silicon layer in relation to the epitaxis layer is achieved through the use of a very low temperature for the deposition of part or all of the buffer layer. Th use of a very low deposition temperature results in improved seeding of the insulating layer and a reduction in the deposition dead time, which makes it possible to produce a thicker layer on the insulating layer than in the active transistor area.