The trench gate or U-groove MOSFET (UMOSFET) has become widely adopted as a semiconductor device globally, gradually replacing the traditional vertical double-diffused MOSFET (DMOSFET) in many applications. Evaluating the reliability of UMOSFETs regarding neutron-induced radiation effects is crucial for understanding their response to ubiquitous atmospheric neutrons. This study presents comparative experimental and computational results of Single-Event Effects induced by monoenergetic fast neutrons in UMOS and DMOS power transistors. Experiments demonstrate that UMOSFETs exhibit premature particle-induced avalanche multiplication effects compared to similarly rated DMOSFETs, which may favor destructive radiation effects, such as Single-Event Burnout, when operating in the terrestrial radiation environment.