Semiconductor device and method of manufacturing the same

A semiconductor device, comprising:

• a semiconductor substrate of the first conduction type;
• a semiconductor region of the first conduction type which is formed on the semiconductor substrate;
• a gate electrode which is provided so that at least part of the gate electrode is present within a trench which is selectively formed in part of the semiconductor region;
• a gate insulating film which is formed between the trench and the gate electrode along a wall surface of the trench;
• a base layer of the second conduction type which is provided on the semiconductor region via the gate insulating film so as to enclose a side wall except a bottom portion of the trench;
• a source region of the first conduction type which is formed adjacent to the gate insulating film outside the trench in the vicinity of a top surface of the base layer;
• and
• a metal film which is formed from a metal or a metal compound and which is provided while maintaining a wide area in a position spaced from a top surface of the source region, which is a top surface of a top end portion of the gate electrode extended from the trench.

A method of manufacturing a semiconductor device including a vertical MOSFET, comprising:

• forming a single crystal semiconductor layer of the first conduction type by an epitaxial growth process on the whole top surface of a single crystal semiconductor substrate of the first conduction type, next forming a base diffusion layer of the second conduction type by repeating photolithography treatment, impurity ion implantation and impurity diffusion on the single crystal semiconductor layer, and selectively forming a source diffusion layer of the first conduction type on a surface of this base diffusion layer;
• forming an oxide film and nitride film on surfaces of the base diffusion layer and the source diffusion layer, then performing patterning to a prescribed shape, and performing etching by use of this patterning as a mask, whereby a trench which pierces through the base diffusion layer and reaches the single crystal semiconductor layer is formed;
• removing the nitride film and then forming an oxide film, which becomes a gate oxide film, on an inner wall surface of the trench and on a top surface of the source diffusion layer;
• depositing a polycrystalline semiconductor film including an impurity of the first conduction type in the trench by being buried in such a manner that the width of the trench and a top end portion protruding upward from the trench satisfy a prescribed relationship, whereby a gate electrode and a top end portion thereof are formed;
• etching an insulating film so as to come into contact with top surfaces of the base layer and the source layer, implanting a base contact layer of the second conduction type in a position adjacent to the source layer by implanting, and thereafter forming a source electrode on top of the source layer and contact layer of the semiconductor substrate;
• and
• forming a drain electrode on a surface opposite to a surface on which the source electrode of the single crystal semiconductor substrate of the first conduction type.