This paper develops measurement procedures for extracting the critical structural parameters of an encapsulated high frequency bipolar transistor from simple measurements. Encapsulated devices can be readily handled and included in a test set up, and the present work obviates the need to fabricate and measure separate simpler test structures for parameter extraction. The parameters extracted are: emitter stripe width and area, epitaxial collector doping, resistivity and width, emitter and collector junction depths, peak base doping, impurity gradient of the emitter junction, oxide thickness and fixed charge, and package parasitic capacitances. The material parameters and the readily observable planar dimensions such as emitter stripe length and metal pad areas are used as input parameters in the extraction procedure. The work re-inforces recent insights into the nature of current flow across the epitaxial collector width of a real device at the onset of base widening effects, as the terminal collector-base voltage is varied. (C) 2002 Elsevier Science Ltd. All rights reserved.