We report a bottom-gate, top-contact vertical-channel In-Ga-Zn-O (IGZO) thin-film transistor (TFT) with a 200-nm channel length defined by vertical stack thickness rather than lithographic critical-dimension control. Conformally RF-sputtered IGZO, together with intentionally nonconformal thermally evaporated Al contacts, enables a self-aligned source/drain formation, whereas a SiO spacer shrinks the gate-drain overlap capacitance by 98% without introducing ungated regions. The resulting devices achieve an on/off current ratio of , a subthreshold swing as low as 118 mV/dec, and a drive current up to 5.34 A/m at = 2 V and = 4 V, matching or surpassing state-of-the-art top-gate vertical IGZO TFTs. Two-dimensional TCAD simulations corroborate the measured electrostatics, clarify charge-control mechanisms in the ultrashort vertical channel, and indicate pathways-such as contact engineering and a thinner IGZO layer-to further enhance on-current flow and saturation. These results indicate that the proposed architecture is a promising candidate for compact active-matrix drivers in next-generation micro-OLED and micro-LED displays.