Abstract: A junction transistor with a collector layer, a base layer and an emitter layer formed in a monocrystalline semiconductor body is provided with an ancillary layer of the same conductivity type as the emitter layer to accelerate the sweep-out of minority carriers at the instant of cutoff, the ancillary and base layers being bridged by a common metallic contact layer. The ancillary layer, which may be divided into several zones, is wholly surrounded by the base layer so as to be bounded by one or more closed lines along a body surface carrying the contact layer, the latter partly or completely overlying these lines. The ancillary and emitter layers may be formed in a single diffusion step through a common mask.