A manufacturing method of a trench power MOSFET is provided. In the manufacturing method, the trench gate structure of the trench power MOSFET is formed in the epitaxial layer and includes an upper doped region, a lower doped region and a middle region interposed therebetween. The upper doped region has a conductive type reverse to that of the lower doped region, and the middle region is an intrinsic or lightly-doped region to form a PIN, P.sup.+/N.sup. or N.sup.+/P.sup. junction. As such, when the trench power MOSFET is in operation, a junction capacitance formed at the PIN, P.sup.+/N.sup. or N.sup.+/P.sup. junction is in series with the parasitic capacitance. Accordingly, the gate-to-drain effective capacitance may be reduced.

In one implementation, a reduced gate charge field-effect transistor (FET) includes a drift region situated over a drain, a body situated over the drift region, and source diffusions formed in the body. The source diffusions are adjacent a gate trench extending through the body into the drift region and having a dielectric liner and a gate electrode situated therein. The dielectric liner includes an upper segment and a lower segment, the upper segment extending to at least a depth of the source diffusions and being significantly thicker than the lower segment.

A semiconductor apparatus includes: a gate electrode in a trench and facing a p type base region with a gate insulating film interposed therebetween on a portion of a side wall; a shield electrode in the trench and between the gate electrode and a bottom of the trench; an electric insulating region in the trench, the electric insulating region extending between the gate electrode and the shield electrode, and further extending along the side wall and the bottom of the trench to separate the shield electrode from the side wall and the bottom; a source electrode electrically connected to an n.sup.+ type source region and the shield electrode. The shield electrode has high resistance regions at positions where the high resistance regions face the side walls of the trench, and a low resistance region at a position where the low resistance region is sandwiched between the high resistance regions.

Provided is a semiconductor apparatus includes: a gate electrode disposed inside a trench and opposedly facing a p type base region with a gate insulating film interposed therebetween on a portion of a side wall; a shield electrode disposed inside the trench and positioned between the gate electrode and a bottom of the trench; an electric insulating region disposed inside the trench, the electric insulating region expanding between the gate electrode and the shield electrode, and further expanding along the side wall and the bottom of the trench so as to separate the shield electrode from the side wall and the bottom; a source electrode electrically connected to an n.sup.+ type source region and the shield electrode, wherein the shield electrode has a high resistance region positioned on an n.sup.+ drain region side, and a low resistance region positioned on a gate electrode side.

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.

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.

A power semiconductor device includes a semiconductor substrate having a drift region, a gate electrode trench in the semiconductor substrate and a field electrode needle trench in the semiconductor substrate. The gate electrode trench extends into the drift region and includes a gate electrode. The gate electrode is arranged in the gate electrode trench and electrically insulated from the drift region by a gate dielectric layer arranged between the gate electrode and the drift region. The field electrode needle trench is laterally spaced from the gate electrode trench and extends into the drift region. The field electrode needle trench includes a field electrode arranged in the field electrode needle trench and electrically insulated from the drift region by a cavity formed between the field electrode and the drift region.

A mask used to form an n.sup.+ source layer (11) is formed by a nitride film on the surface of a substrate before a trench (7) is formed. At this time, a sufficient width of the n.sup.+ source layer (11) on the surface of the substrate is secured. Thereby, stable contact between the n.sup.+ source layer (11) and a source electrode (15) is obtained. A CVD oxide film (12) that is an interlayer insulating film having a thickness of 0.1 micrometer or more and 0.3 micrometer or less is formed on doped poly-silicon to be used as a gate electrode (10a) embedded in the trench (7), and non-doped poly-silicon (13) that is not oxidized is formed on the CVD oxide film (12). Thereby, generation of void in the CVD oxide film (12) is suppressed and, by not oxidizing the non-doped poly-silicon (13), a semiconductor apparatus is easily manufactured.