Abstract: A semiconductor device has a first conductivity type semiconductor substrate, a second conductivity type buried layer formed in a predetermined region on the semiconductor substrate, and a first conductivity type epitaxial growth layer formed on the buried layer and the semiconductor substrate. Trenches are formed in the epitaxial growth layer and arranged side by side in a gate width direction of a transistor to be formed. An entire bottom surface of each trench is entirely surrounded by and disposed in contact with the buried layer. A gate electrode is formed inside and on a top surface of each of the trenches and on a surface of the epitaxial growth layer adjacent to each of the trenches via a gate insulating film. A second conductivity type high concentration source diffusion layer is formed on one side of the gate electrode. A second conductivity type high concentration drain diffusion layer formed on another side of the gate electrode.

Abstract: The semiconductor device includes a trench having a depth of a distance equal to or shorter than the L length of the transistor, and a buried layer is used in a bottom portion of the trench, whereby an effective channel length from each of a lower end of a high concentration source diffusion layer and a lower end of a high concentration drain diffusion layer to a bottom surface of the trench is made shorter than the shortest length L on a top surface of the trench. Accordingly, a current path is held on the bottom surface of the trench from a side surface thereof which contacts with the source or high concentration drain diffusion layer with a use of the buried layer, whereby the driving performance is enhanced. An effect of suppressing the decrease of the driving performance is obtained for the reduced gate length.

Abstract: Provided is a semiconductor device formed with a trench portion for providing a concave portion in a gate width direction and with a gate electrode provided within and on a top surface of the trench portion via a gate insulating film. At least a part of a surface of each of the source region and the drain region is made lower than other parts of the surface by removing a thick oxide film formed in the vicinity of the gate electrode. Making lower the part of the surface of each of the source region and the drain region allows current flowing through a top surface of the concave portion of the gate electrode at high concentration to flow uniformly through the entire trench portion, which increase an effective gate width of the concave portion formed so as to have a varying depth in a gate width direction.

Abstract: Provided is a semiconductor device formed with a trench portion for providing a concave portion having a continually varying depth in a gate width direction and with a gate electrode provided within the trench portion and on a top surface thereof via a gate insulating film. Before the formation of the gate electrode, an impurity is added to at least a part of the source region and the drain region by ion implantation from an inner wall of the trench portion, and then heat treatment is performed for diffusion and activation to form a diffusion region from the surface of the trench portion down to a bottom portion thereof. Current flowing through a top surface of the concave portion of the gate electrode at high concentration can flow uniformly through the entire trench portion.