We present a direct approach to obtain scattering parameters (S-parameters) and other derived figures of merit of SiGe-HBTs by means of small-signal (ac) analysis. Therefore, an additional simulation mode has been implemented in the three-dimensional device simulator MINIMOS-NT. Several additional features are provided for efficiently obtaining various small-signal parameters. The accuracy of the results is proven by analytical methods and by comparison with measurements. (C) 2003 Elsevier B.V. All rights reserved.