Structure of trench metal-oxide-semiconductor field-effect transistor

A structure of a trench metal-oxide-semiconductor field-effect transistor (UMOSFET), the structure comprising:

• a metal layer disposed on a top surface and a bottom surface of the structure to form a source and a drain, respectively, to function as electrodes of the structure connected to an external device;
• an N-type semiconductor substrate disposed on the drain;
• an N-drift region disposed on the N-type semiconductor substrate;
• an N-current spread layer (N-CSL) disposed on the N-drift region;
• a P-well disposed on the N-CSL;
• an N-type semiconductor layer disposed on the P-well;
• a first P-type semiconductor layer adjacent to the N-type semiconductor layer and disposed on the P-well;
• a trench extending through the N-type semiconductor layer, the P-well and the N-CSL, wherein a bottom of the trench terminates at the N-drift region;
• an insulating layer disposed in the trench;
• a split gate disposed in the insulating layer of the trench and covered by the insulating layer;
• a gate disposed in the insulating layer of the trench and above the split gate;
• and
• a semiconductor protection layer disposed below the bottom of the trench and adjacent to the N-drift region, wherein the insulating layer is disposed above the semiconductor protection layer to protect the insulating layer from being broken through by an electric field when the structure turns off a bias;
• wherein the gate and the split gate are separated from each other by the insulating layer to form a predetermined gap;
• and a depth position of a bottom of the gate is deeper than an interface between the P-well and the N-CSL;
• wherein the insulating layer is disposed between a bottom surface of the split gate and the semiconductor protection layer.