Semiconductor device and method of manufacturing the same
A semiconductor device has an active region in which a plurality of unit cells are regularly arranged, each of the unit cells including: a channel region having a first conductivity type and formed over a front surface of a semiconductor substrate; a source region having a second conductivity type different from the first conductivity type and formed over the front surface of the semiconductor substrate in such a manner as to be in contact with the channel region; and a JFET region having the second conductivity type and is formed over the front surface of the semiconductor substrate on the opposite side of the channel region from the source region in such a manner as to be in contact with the channel region. The channel region is comprised of a first channel region and a second channel region higher than the first channel region in impurity concentration, over the front surface of the semiconductor substrate.
1. A semiconductor device having an active region in which a plurality of unit cells are regularly arranged, each of the unit cells comprising:
a channel region formed over a front surface of a semiconductor substrate and having a first conductivity type;
a source region having a second conductivity type different from the first conductivity type and formed over the front surface of the semiconductor substrate so as to be in contact with the channel region; and
a JFET region having the second conductivity type and formed over the front surface of the semiconductor substrate on an opposite side of the channel region from the source region such as to be in contact with the channel region,
wherein the channel region is comprised of a first channel region and a second channel region higher than the first channel region in impurity concentration, and
wherein said first and second channel regions are arranged along first and second directions, respectively, so as to surround outer edge portions of said source region of each said unit cell in a plan view.
2. The semiconductor device according to claim 1 ,
wherein the impurity concentration of the second channel region is 1.6 to 2.5 times the impurity concentration of the first channel region.
3. The semiconductor device according to claim 1 ,
wherein the unit cell is rectangular or square in shape.
4. The semiconductor device according to claim 1 ,
wherein the JFET region is a rectangular region,
the first channel region is formed along an edge of the JFET region, and
the second channel region is formed in contact with a vertex of the JFET region.
5. The semiconductor device according to claim 1 ,
wherein the JFET region is surrounded by the channel region.
6. The semiconductor device according to claim 1 ,
wherein the source region constituting the unit cell is formed in such a manner that the source regions of the adjacent unit cells are separate from each other, and is octagonal in shape.
7. The semiconductor device according to claim 6 ,
wherein edges constituting the octagon have two or three kinds of lengths, the first channel region is formed along a longest edge, and the second channel region is formed along a shortest edge.
8. The semiconductor device according to claim 6 ,
wherein a channel length of the first channel region is 1.1 to 1.7 times the channel length of the second channel region.
9. The semiconductor device according to claim 1 , comprising:
a gate insulating film formed over the channel region and at least part of the source region;
a gate electrode formed over at least part of the gate insulating film;
a body region having the first conductivity type and formed under the source region;
a body contact region having the first conductivity type, formed in contact with the body region and higher than the body region in impurity concentration;
a source electrode in contact with the body contact region; and
a drain electrode formed on a surface opposite to the front surface of the semiconductor substrate.