Results of conductance measurements in 0.2-mu-m-wide and 0.15-mu-m-long silicon metal-oxide-semiconductor field-effect transitions with shallow-trench isolations are presented. At T = 1.2 K, two kinds of periodic conductance fluctuations are observed; fine structure near threshold and plateaus in the higher conductance regime (approximately 0.1 mS). The latter are accentuated by applying moderate magnetic fields of 1-2 T, remaining unchanged in their positions. We attribute these features to a quasi-one-dimensional transport mechanism caused by strain-induced narrow potential wells along the trench isolations.