Enabling a Compact Model to Simulate the RF Behavior of MOSFETs in SPICE Reydezel Torres-Torres, Roberto Murphy-Arteaga Instituto Nacional de Astrofı´sica, O ´ ptica y Electro ´ nica–INAOE, Departamento de Electro ´ nica, A. P. 51 & 216, 72000, Puebla, Mexico Received 26 July 2004; accepted 8 November 2004 ABSTRACT: A detailed methodology for implementing a MOSFET model valid to perform RF simulations is described in this article. Since the SPICE-like simulation programs are used as a standard tool for integrated circuit (IC) design, the resulting model is oriented for its application under the SPICE environment. The core of the proposed model is the popular BSIM3v3, but in this model the RF effects are taken into account by means of extrinsic lumped elements. Good agreement between the simulated and measured small-signal S-parameter data is achieved for a 0.18-m channel-length MOSFET, thus validating the proposed model. © 2005 Wiley Periodicals, Inc. Int J RF and Microwave CAE 15: 255–263, 2005. Keywords: RF-CMOS; MOSFET; BSIM; semiconductor device modeling I. INTRODUCTION Nowadays, CMOS devices fabricated on silicon sub- strates are used in commercial RF/microwave ICs [1, 2]. As a consequence, new models for the represen- tation of MOSFET behavior at high frequencies are being demanded by industry. Furthermore, IC design- ers require models to analyze their circuits under both DC and RF regimes. Due to their reliability, the compact models represent a viable alternative to per- form this job. Even though BSIM4 — which is an extension of BSIM3v3 — has already been launched by the Uni- versity of California at Berkeley [3], BSIM3v3 is still one of the most widely used compact models by the IC industry. This is due to the fact that BSIM3v3 properly represents the DC characteristics of sub- 0.25-m MOSFETs, whereas the use of BSIM4 is recommended only for sub-100-nm devices, in which advanced features such as a considerable gate leakage current should be taken into account. Although BSIM3v3 includes good current–voltage and capacitance models, it neglects the distributed effects associated with a MOSFET, which become important when the operation frequency rises. This introduces errors in simulations when the MOSFET is operating in the RF regime. The most important ef- fects to be considered in a good RF model are those associated with the device’s terminals. Hence, the gate, source, drain, and substrate resistances need to be added externally to BSIM3v3 in order to enable it to perform RF simulations. For this reason, several methods to enable BSIM3v3 to perform high-fre- quency simulations have been proposed [4 –7]. How- ever, these approaches do not include a detailed and clarified methodology to perform the model imple- mentation. Moreover, the maximum frequency at which previous BSIM3v3-based RF models are vali- dated is 10 GHz. In this article, a procedure to implement an RF MOSFET model using BSIM3v3 is presented, and the required modifications to the original model are pre- sented in detail. This model is validated by achieving Correspondence to: R. Torres-Torres; email: reydezel@inaoep.mx. DOI 10.1002/mmce.20080 Published online 7 March in Wiley InterScience (www.interscience. wiley.com). © 2005 Wiley Periodicals, Inc. 255