1. A powder magnetic core, comprising:
a bulk body containing a main component of a powder of an Fe-base alloy having a soft magnetic property, and the balance including a heat-treated insulation binder and a void,
wherein an aspect ratio of said powder is in a range of 1 to 1.5, and a volume ratio of said powder in said bulk body is in a range of 40 to 60 volume %, and
an initial permeability (\u03bc0) has a value which satisfies 6\u2266\u03bc0\u226620, and a relation of \u03bc\u03bc0\u22670.5 is established between \u03bc0 and \u03bc, when the permeability is \u03bc with an applied magnetic field of 24 kAm.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A wide band gap semiconductor device comprising:
a first conductivity type semiconductor substrate having a high impurity concentration;
a first conductivity type drift layer having a lower impurity concentration than the semiconductor substrate and formed on one principal surface of the semiconductor substrate;
a second conductivity type base layer having a higher impurity concentration than the drift layer and formed on the drift layer; and
a first conductivity type source region selectively disposed on a principal surface of the base layer;
a first trench having a depth extending from a principal surface of the source region to reach the drift layer;
a control electrode which is filled through a gate insulating film in the first trench so as to be located in a position facing the source region, the base layer and the drift layer;
a second trench provided near the first trench and having a depth extending from the principal surface of the base layer to reach the drift layer so as to be deeper than the first trench, wherein the second trench has a circular pattern so that a surface pattern of the first trench is surrounded by a surface of the second trench;
a first main electrode which is disposed in the second trench to form a Schottky junction between the first main electrode and a surface of the drift layer located in the second trench so that the first main electrode covers both the principal surface of the source region and the principal surface of the base layer; and
a second main electrode which is disposed on the other principal surface of the first conductivity type semiconductor substrate.
2. A wide band gap semiconductor device according to claim 1, further comprising a second conductivity type region being in contact with a bottom of the second trench.
3. A wide band gap semiconductor device according to claim 1, wherein the distance between central lines of the first and second trenches is not longer than 10 \u03bcm.
4. A wide band gap semiconductor device according to claim 3, wherein the wide band gap semiconductor device uses silicon carbide semiconductor as a main semiconductor material.
5. A wide band gap semiconductor device according to claim 3, wherein the wide band gap semiconductor device uses gallium nitride semiconductor as a main semiconductor material.
6. A wide band gap semiconductor device according to claim 1, further comprising:
an active region at least having the first trench;
a peripheral voltage withstanding structure portion which surrounds the active region and which has circular third trenches each of which is filled with an insulating film; and
metal electrodes which are disposed on a surface of the second conductivity type base layer so as to be located between the third trenches.