Semiconductor device and manufacturing method thereof and power supply apparatus using the same
A semiconductor device comprises a trench-gate type field-effect transistor on a semiconductor substrate having a first main surface and a second main surface oppositely positioned in a thickness direction, wherein the trench-gate type field-effect transistor comprises a first semiconductor region at the first main surface side; a second semiconductor region at the second main surface; a semiconductor well region between the first semiconductor region and the second semiconductor region; a trench formed so as to protrude in a first direction intersecting the second main surface; a gate electrode formed on an inner surface of the trench via a gate insulating film, and a bottom of the gate electrode is in the first semiconductor region, and a well bottom has a well deep portion and a well shallow portion, and the well deep portion is in a region more distant from the gate insulating film compared to the well shallow portion.
1 . A semiconductor device comprising a trench-gate type field-effect transistor on a semiconductor substrate having a first main surface and a second main surface oppositely positioned in a thickness direction, the trench-gate type field-effect transistor comprising:
a first semiconductor region for a drain provided at a first main surface side of the semiconductor substrate and having a first conductivity type;
a second semiconductor region for a source provided at a second main surface side of the semiconductor substrate and having the first conductivity type;
a semiconductor well region provided between the first semiconductor region and the second semiconductor region and having a second conductivity type whose polarity of carrier is opposite to a polarity of the first conductivity type;
a trench formed so as to protrude from the second main surface in a first direction intersecting the second main surface of the semiconductor substrate;
a gate insulating film formed on an inner surface of the trench; and
a gate electrode formed so as to cover the gate insulating film and fill the trench,
wherein a bottom of the gate electrode is in the first semiconductor region.
2 . The semiconductor device according to claim 1 ,
wherein a well bottom, as a junction between the semiconductor well region and the first semiconductor region, has a well deep portion with a comparatively long distance from the second main surface of the semiconductor substrate to the well bottom along the first direction, and a well shallow portion with a comparatively short distance therefrom, and
the well deep portion is in a region more distant from the gate insulating film compared to the well shallow portion.
3 . The semiconductor device according to claim 2 ,
wherein a gate electrode protrusion distance being a length of a part of the gate electrode existing in the first semiconductor region along the first direction is 20% or more of a gate electrode depth being a distance from the second main surface of the semiconductor substrate to the bottom of the gate electrode.
4 . The semiconductor device according to claim 2 ,
wherein, in the well bottom, a depth of the well deep portion being a distance from the second main surface of the semiconductor substrate to the well deep portion along the first direction is 80% or more of a gate electrode depth being a distance from the second main surface of the semiconductor substrate to the bottom of the gate electrode.
5 . The semiconductor device according to claim 2 ,
wherein a channel length along the first direction in a channel region which is a junction with the gate insulating film in the semiconductor well region is 1 μm or less.
6 . A method of manufacturing a semiconductor device comprising a trench-gate type field-effect transistor, comprising the steps of:
(a) preparing a semiconductor substrate having a first main surface and a second main surface oppositely positioned in a thickness direction, and a first semiconductor region with a first conductivity type;
(b) forming a trench protruding from the second main surface in a first direction intersecting the second main surface of the semiconductor substrate after the step (a);
(c) forming a gate insulating film on an inner surface of the trench after the step (b);
(d) forming a gate electrode so as to cover the gate insulating film and fill the trench after the step (c);
(e) forming a semiconductor well region by introducing impurities of a second conductivity type whose polarity of carrier is opposite to a polarity of the first conductivity type from the second main surface of the semiconductor substrate after the step (d); and
(f) forming a second semiconductor region by introducing impurities of the first conductivity type from the second main surface of the semiconductor substrate after the step (e),
wherein a bottom of the gate electrode is in the first semiconductor region, and
a gate electrode protrusion distance being a length of a part of the gate electrode existing in the first semiconductor region along the first direction is 20% or more of a gate electrode depth being a distance from the second main surface of the semiconductor substrate to the bottom of the gate electrode.
7 . The method of manufacturing a semiconductor device according to claim 6 ,
wherein, after the step (e), a protective film is formed to integrally cover exposed portions of the gate insulating film and the gate electrode and a part of a surface of the semiconductor well region adjacent thereto within the second main surface of the semiconductor substrate,
then a well deep portion is formed by introducing impurities of the second conductivity type so as to reach a deeper region in the first direction than the semiconductor well region formed in the step (e), and thereafter, the step (f) is carried out, and
in the well deep portion, a depth of the well deep portion being a distance from the second main surface of the semiconductor substrate to a junction of the first semiconductor region along the first direction is 80% or more of the gate electrode depth.
8 . A power supply apparatus of synchronous rectification type for supplying a power to a semiconductor device, the power supply apparatus comprising:
a first field-effect transistor; and
a second field-effect transistor,
wherein the first field effect transistor or the second field effect transistor is a trench-gate type field-effect transistor formed on a semiconductor substrate having a first main surface and a second main surface oppositely positioned in a thickness direction, and
the trench-gate type field-effect transistor comprises:
a first semiconductor region for a drain provided at a first main surface side of the semiconductor substrate and having a first conductivity type;
a second semiconductor region for a source provided at a second main surface side of the semiconductor substrate and having the first conductivity type;
a semiconductor well region provided between the first semiconductor region and the second semiconductor region and having a second conductivity type whose polarity of carrier is opposite to a polarity of the first conductivity type;
a trench formed so as to protrude from the second main surface in a first direction intersecting the second main surface of the semiconductor substrate;
a gate insulating film formed on an inner surface of the trench; and
a gate electrode formed so as to cover the gate insulating film and fill the trench,
wherein a bottom of the gate electrode is in the first semiconductor region, and
a gate electrode protrusion distance being a length of a part of the gate electrode existing in the first semiconductor region along the first direction is 20% or more of a gate electrode depth being a distance from the second main surface of the semiconductor substrate to the bottom of the gate electrode.
9 . The power supply apparatus according to claim 8 ,
wherein a well bottom, as a junction between the semiconductor well region and the first semiconductor region, has a well deep portion with a comparatively long distance from the second main surface of the semiconductor substrate to the well bottom along the first direction and a well shallow portion with a comparatively short distance therefrom,
the well deep portion is in a region more distant from the gate insulating film compared to the well shallow portion, and,
in the well deep portion, a depth of the well deep portion being a distance from the second main surface of the semiconductor substrate to the well bottom along the first direction is 80% or more of the gate electrode depth.