Device-modeling techniques for high-frequency circuits operated at over 100 GHz is presented. When the MOSFET model included in the process design kit (PDK) is used, difference between the simulated and measured gain of a low-noise amplifier is about 9.1 dB at 120 GHz. To improve accuracy of the simulation, device models for the bond-based design  are introduced. For the MOSFET model, external transmission lines, capacitors and inductors are added to the original MOSFET model. And, the values of these external elements are extracted so that the simulated S-parameters are fit to the measured ones. When the proposed models are used, the difference between the simulated and measured gain of the low-noise amplifier is improved to less than 0.6 dB at 120 GHz.