<p>In nanoscale semiconductor devices, not only do electron–electron interactions require proper treatment but heat transport must also be integrated coherently. In this Perspective, we propose a paradigm shift: to treat electron transport using a three-part phase diagram that includes diffusive, ballistic and viscous electron-fluid regimes and to adopt a statistical-field approach to extend the tools for analysis, including the drift–diffusion model. The statistical-field approach posits that semiconductor devices — as open quantum systems characterized by fluctuating energy and particle numbers — can achieve local equilibrium through frequent microscopic collisions of electrons. The corresponding statistical fields emerge — specifically, spatial and temporal variations in temperature and chemical potential, which dictate the flows of energy and particles. The quantum nature of these statistical fields enables a seamless integration of quantum complexities, and the approach naturally incorporates heat dissipation in a self-consistent theoretical framework (although the proper modelling of boundary conditions requires further attention). We highlight the critical need to identify the transport regime in which short-channel nanodevices operate, to be able to build accurate simulators that will drive device design and optimization.</p>