Trench-gate field effect transistor

A trench-gate field effect transistor, comprising:

• an epitaxial lamination structure which includes an epitaxial substrate having a first conductive type, an epitaxial layer disposed on said epitaxial substrate and having the first conductive type, a plurality of mesa regions disposed in said epitaxial layer and spaced apart from each other in a first direction, a plurality of well regions having a second conductive type and formed downwardly from top surfaces of said mesa regions, respectively, and a plurality of source electrodes having the first conductive type and disposed in said well regions, respectively;
• a plurality of trenches which are recessed downwardly from a top surface of said epitaxial layer, which extend in a second direction transverse to the first direction, and which are spaced apart from each other in the first direction, each of said trenches having a first trench region extending in the second direction and having a width in the first direction, a second trench region extending in the second direction and having a width in the first direction smaller than the width of said first trench region, and a neck trench region extending between said first trench region and said second trench region and having a width in the first direction decreasing gradually along the second direction from the width of said first trench region to the width of said second trench region, each of said trenches having an upper trench portion and a lower trench portion disposed below and spatially communicating with said upper trench portion in a depth direction transverse to the first and second directions, each of said mesa regions being disposed between two corresponding ones of said trenches;
• a plurality of gate electrode units, each of which is disposed in said upper trench portion of a corresponding one of said trenches, and each of which includes a pair of first gate electrode portions disposed in said first trench region of a corresponding one of said trenches and spaced apart from each other in the first direction, a pair of second gate electrode portions disposed in said neck trench region of said corresponding one of said trenches, and a third gate electrode portion disposed in said second trench region of said corresponding one of said trenches, such that each of said second gate electrode portions interconnects a corresponding one of said first gate electrode portions and said third gate electrode portion;
• a plurality of source electrode units which are disposed in said trenches, respectively, each of said source electrode units including a first source electrode portion disposed between a pair of said first gate electrode portions of a corresponding one of said gate electrode units, and a second source electrode portion connected to said first source electrode portion, said first source electrode portion having a top end surface at a same level with said top surface of said epitaxial layer and extending downwardly in the depth direction from said top end surface into said lower trench portion, said second source electrode portion being connected to a lower part of said first source electrode portion disposed in said lower trench portion and extending through said neck trench region to said second trench region;
• a plurality of insulation units which are disposed in said trenches, respectively, and which cover said gate electrode units and said source electrode units, respectively;
• an isolation unit which is disposed on said epitaxial layer and which has an electric insulating property;
• a contact electrode unit which includes a first contact electrode electrically connected to said third gate electrode portion of each of the gate electrode units and a second contact electrode electrically connected to said source electrodes and said source electrode units;
• and
• a drain electrode which is disposed on said epitaxial substrate opposite to said epitaxial layer.