Terrestrial single-event transients (SETs) are mainly induced by secondary ions of neutron-induced nuclear reactions, which do not cross the sensitive drain in most cases. Technology computer-aided design (TCAD) simulations show that in those cases, both diffusion-collection current and burst-plateau-type current waveform could occur in nanoscale complementary metal-oxide-semiconductor (CMOS) technology. The necessity of including recombination effect in diffusion-collection model is identified, and an equivalent circuit model (ECM) is established to describe SETs induced by secondary ions with short distance to the drain. Both models are verified by TCAD simulations.