The electro-thermal behavior of a bulk CMOS device is analyzed using the hydrodynamic model equation. The analysis is first applied to an introductory example of a single field-effect-transistor (FET) to indicate the importance of incorporating a non-equilibrium state between charge carriers and phonons in the analytical model. Then, the system of hydrodynamic model equations is described in detail, which takes into account carrier generation/recombination process and non-equilibrium between charge carriers and phonons. A supposed bulk CMOS device has nano-meter dimensions and thus is vulnerable to malfunction due to crosstalk between the constituent FETs. The simulation of electro-thermal transients in the entire CMOS domain is performed focusing on the behavior in a short period after switching of the gate voltage from low to high. The result shows a significant level of crosstalk that may lead to impairment of the switching function of the CMOS. Also shown is the development of a hot spot at the source region of the activated FET in addition to the one at the gate/drain corner. The deliberate omission of sub-continuum mechanisms, particularly the carrier generation/recombination, from the analytical model produced erroneous distributions of charge carrier density and temperature, thus proving the significance of this mechanism in defining heat generation and heat flow in the device.