Abstract: A diode has a semiconductor layer of a first conductive type having a first principal plane and a second principal plane facing the first principal plane; a first impurity layer of a second conductive type which is opposite to said first conductive type, said first impurity layer being selectively formed on said first principal plane of said semiconductor layer; a second impurity layer of the first conductive type which is selectively formed on said first principal plane of said semiconductor layer apart from said first impurity layer; a first main electrode connected to said first impurity layer; a second main electrode connected to said second impurity layer; a third impurity layer of the first conductive type which is selectively formed on said second principal plane of said semiconductor layer and which is formed so as to face said first impurity layer; a fourth impurity layer of the second conductive type which is selectively formed on said second principal plane of said semiconductor layer and which is

Abstract: A semiconductor device includes: a semiconductor substrate, at least a surface portion thereof serving as a low-resistance drain layer of a first conductivity type; a first main electrode connected to the low-resistance drain layer; a high-resistance epitaxial layer of a second-conductivity type formed on the low-resistance drain layer; a second-conductivity type base layer selectively formed on the high-resistance epitaxial layer; a first-conductivity type source layer selectively formed in a surface portion of the second-conductivity type base layer; a trench formed in a region sandwiched by the second-conductivity type base layers with a depth extending from the surface of the high-resistance epitaxial layer to the semiconductor substrate; a jfet layer of the first conductivity type formed on side walls of the trench; an insulating layer formed in the trench; an LDD layer of the first-conductivity type formed in a surface portion of the second-conductivity type base layer so as to be connected to the first

Abstract: A diode has a semiconductor layer of a first conductive type having a first principal plane and a second principal plane facing the first principal plane; a first impurity layer of a second conductive type which is opposite to said first conductive type, said first impurity layer being selectively formed on said first principal plane of said semiconductor layer; a second impurity layer of the first conductive type which is selectively formed on said first principal plane of said semiconductor layer apart from said first impurity layer; a first main electrode connected to said first impurity layer; a second main electrode connected to said second impurity layer; a third impurity layer of the first conductive type which is selectively formed on said second principal plane of said semiconductor layer and which is formed so as to face said first impurity layer; a fourth impurity layer of the second conductive type which is selectively formed on said second principal plane of said semiconductor layer and which is

Abstract: A semiconductor device comprises a main switching element, an electric field detector and an on-voltage application unit. The main switching element includes a high-voltage main electrode, at least a low-voltage main electrode and at least a first gate electrode. The electric field detector has a MOS structure making conductive between the high-voltage main electrode and the first gate electrode in a path other than the main switching element in accordance with a predetermined electric field generated in the main switching element. The on-voltage application unit applies an on-voltage to the first gate electrode on the basis of the conductive state.

Abstract: Optical fibers are fixed to elongating tables by optical fiber fixing jigs. Coatings are removed from portions of the fibers and respective fibers of two different groups are placed into tight contact with one another. The fibers are then heated by a gas burner 4A so as to be welded integrally with each other, and are then elongated. In one preferred embodiment, the fibers are arranged such that there are gaps therebetween. These gaps are substantially 250 .mu.m. The gaps are sufficiently wide that heating gas flows in a manner such that all the optical fiber strands are heated uniformly to make it possible uniform welding and elongation.

Abstract: Optical fibers are fixed to elongating tables by optical fiber fixing jigs. Coatings are removed from portions of the fibers and respective fibers of two different groups are placed into tight contact with one another. Rectifier rods, supported movably by rectifier rod supporting members, are disposed outside the optical fiber strands. The fibers are then heated by a gas burner 4A so as to be welded integrally with each other, and are then elongated. By using rectifier rods, the outside optical fiber strands of the groups being welded are not so strongly heated that uniform welding and elongation can be realized. In one preferred embodiment, the fibers are arranged such that there are gaps therebetween. These gaps are substantially 250 .mu.m. The gaps are sufficiently wide that heating gas flows in a manner such that all the optical fiber strands are heated uniformly to make it possible uniform welding and elongation.