Semiconductor devices includes a thin epitaxial layer (nanotube) formed on sidewalls of mesas formed in a semiconductor layer. In one embodiment, a semiconductor device includes a first semiconductor layer, a second semiconductor layer formed thereon and of the opposite conductivity type, and a first epitaxial layer formed on mesas of the second semiconductor layer. An electric field along a length of the first epitaxial layer is uniformly distributed.

Various improvements in vertical transistors, such as IGBTs, are disclosed. The improvements include forming periodic highly-doped p-type emitter dots in the top surface region of a growth substrate, followed by growing the various transistor layers, followed by grounding down the bottom surface of the substrate, followed by a wet etch of the bottom surface to expose the heavily doped p+ layer. A metal contact is then formed over the p+ layer. In another improvement, edge termination structures utilize p-dopants implanted in trenches to create deep p-regions for shaping the electric field, and shallow p-regions between the trenches for rapidly removing holes after turn-off. In another improvement, a dual buffer layer using an n-layer and distributed n+ regions improves breakdown voltage and saturation voltage. In another improvement, p-zones of different concentrations in a termination structure are formed by varying pitches of trenches. In another improvement, beveled saw streets increase breakdown voltage.

Provided is a semiconductor device comprising: a semiconductor substrate; a plurality of gate trench sections formed in the semiconductor substrate; and a plurality of emitter trench sections formed in the semiconductor substrate, one or more emitter trench sections provided in each region between adjacent gate trench sections of the plurality of gate trench sections, wherein the semiconductor device includes at least one of: pairs of gate trench sections in which at least two gate trench sections of the plurality of gate trench sections are connected; and a pair of emitter trench sections in which at least two emitter trench sections of the plurality of emitter trench sections are connected.

A semiconductor device includes: a semiconductor substrate; a main electrode; a peripheral electrode; an insulating protective film; a surface metallic layer; and a solder layer, wherein the semiconductor substrate includes: a first region of a first conductive-type in contact with the main electrode on a main contact surface; a second region of a first conductive-type in contact with the peripheral electrode on a peripheral contact surface; and a third region of a second conductive-type provided under the first region, under the second region, and circumferentially outward of the second region, and a circumferentially-outward end of the metallic layer and a circumferentially-outward end of the solder layer are located more circumferentially inward than the circumferentially-outward end of the peripheral electrode.

A semiconductor device includes: an FET structure that is formed next to a looped trench on a semiconductor substrate and that has an n.sup.+ emitter region and an n.sup. drain region facing each other in the depth direction of the looped trench across a p-type base region; a p-type floating region formed on the side of the looped trench opposite to the FET structure; and an emitter connecting part that is electrically connected to the n.sup.+ emitter region and a trench gate provided in the same trench, the emitter connecting part and the trench gate being insulated from each other by the looped trench. The trench gate faces the FET structure, and the emitter connecting part faces the p-type floating region, across an insulating film.

A semiconductor device includes a semiconductor substrate comprising a main surface and a gate electrode in a trench between neighboring semiconductor mesas, The gate electrode is electrically insulated from the neighboring semiconductor mesas by a dielectric layer. The semiconductor device further includes a conductor arranged, at least partially, between neighboring dielectric contact spacers. The conductor has a conductivity greater than a conductivity of the gate electrode, An interface between the conductor and the gate electrode extends along the gate electrode.

In one embodiment, a power MOSFET cell includes an N+ silicon substrate having a drain electrode. An N-type drift layer is grown over the substrate. An N-type layer, having a higher dopant concentration than the drift region, is then formed along with a trench having sidewalls. A P-well is formed in the N-type layer, and an N+ source region is formed in the P-well. A gate is formed over the P-well's lateral channel and has a vertical extension into the trench. A positive gate voltage inverts the lateral channel and increases the vertical conduction along the sidewalls to reduce on-resistance. A vertical shield field plate is also located next to the sidewalls and may be connected to the gate. The field plate laterally depletes the N-type layer when the device is off to increase the breakdown voltage. A buried layer and sinker enable the use of a topside drain electrode.

In some aspects of the invention, an n-type field-stop layer can have a total impurity of such an extent that a depletion layer spreading in response to an application of a rated voltage stops inside the n-type field-stop layer together with the total impurity of an n.sup. type drift layer. Also, the n-type field-stop layer can have a concentration gradient such that the impurity concentration of the n-type field-stop layer decreases from a p.sup.+ type collector layer toward a p-type base layer, and the diffusion depth is 20 m or more. Furthermore, an n.sup.+ type buffer layer of which the peak impurity concentration can be higher than that of the n-type field-stop layer at 610.sup.15 cm.sup.3 or more, and one-tenth or less of the peak impurity concentration of the p.sup.+ type collector layer, can be included between the n-type field-stop layer and p.sup.+ type collector layer.

An improvement is achieved in the performance of a semiconductor device. The semiconductor device includes a first trench gate electrode and second and third trench gate electrodes located on both sides of the first trench gate electrode interposed therebetween. In each of a semiconductor layer located between the first and second trench gate electrodes and the semiconductor layer located between the first and third trench gate electrodes, a plurality of p.sup.+-type semiconductor regions are formed. The p.sup.+-type semiconductor regions are arranged along the extending direction of the first trench gate electrode in plan view to be spaced apart from each other.

The surface of an interlayer insulating film formed over an emitter coupling portion and the surface of an emitter electrode formed over the interlayer insulating film are caused to have a gentle shape, in particular, at the end of the emitter coupling portion, by forming the emitter coupling portion over a main surface of a semiconductor substrate and integrally with trench gate electrodes in order to form a spacer over the sidewall of the emitter coupling portion. Thereby, stress is dispersed, not concentrated in an acute angle portion of the emitter coupling portion when an emitter wire is coupled to the emitter electrode (emitter pad), and hence occurrence of a crack can be suppressed. Further, by forming the spacer, the concavities and convexities to be formed in the surface of the emitter electrode can be reduced, whereby the adhesiveness between the emitter electrode and the emitter wire can be improved.