NOVELTY - The method involves forming a main epitaxial (epi) layer atop a substrate. Multiple trench bottom oxide (TBO) layers are formed in multiple trench areas atop the main epi layer and including depositing a poly film in the trench areas. An auxiliary epi layer is grown by a merged epitaxial lateral overgrowth (MELO) step atop the TBO layers and after formation of TBO layers. A portion of the auxiliary epi layer is etched by plasma dry etching with an end point mode according to locations of the TBO layers to form multiple trenches for the trench MOSFET (610).    USE - Method for fabricating trench metal oxide semiconductor field effect transistor (MOSFET) in upward direction, for use as switch in power conversion system such as direct current/direct current (DC-DC) converter, an alternating current (AC)-DC converter, or DC-AC converter for use in product such as notepad and smartphone for battery power management, and DC-DC conversion.    ADVANTAGE - A predetermined uniform trench depth, a thicker TBO layer without stress, and a uniform epi thickness across the entire epi layer can be achieved since MELO step is performed to grow the rest of the epi thickness of the trench MOSFET. Poly seal can be performed after the formation of TBO layers and before a MELO step to improve quality and purity of auxiliary epi layer formed in the MELO step. Plasma dry etching with an end point mode can be performed according to the locations of TBO layers to improve the uniformity of trench depth. The trenches of the trench MOSFET are formed, and the variations in the uniformity of trench depth across the wafer can be significantly reduced to less than 1% by using end points to etch the trenches. The predetermined epi thickness for the trench MOSFET is easier to achieve to sustain a breakdown voltage (BV) of the trench MOSFET. The polysilicon layers act as caps atop the oxide layers to seal out oxygen gas in the MELO step, which can reduce the number of oxygen atoms incorporated into the silicon epi process and improve the quality of the epi layer. The upward fabrication processes of the trench MOSFET make the parameters, e.g., the implant profile, shape and thickness, of each layer easier to control. Hence, extra fabrication steps are avoided, and the cost of fabricating the trench MOSFET is reduced. Due to the improved uniformity and silicon epi purity, and the reduced fabrication processes of the trench MOSFET, the switch has relatively higher quality and lower cost.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic block diagram of a power conversion system.    Power conversion system (600)    Trench MOSFET (610)