Abstract: An impurity concentration profile that improves pn junction breakdown voltage and mitigates the electric field, and that does not adversely affect the characteristics of a field effect transistor is realized. An n type source/drain region is formed at a silicon substrate. A p type impurity concentration profile. includes respective peak concentrations at a dope region for forming a p type well, a p type channel cut region, and a p type channel dope region. An impurity concentration profile of the n type source/drain region crosses the p type impurity concentration profile at a low concentration, and includes phosphorus implantation regions indicating impurity concentrations respectively higher than those of the p type channel cut region and the p type channel dope region and respective peaks in impurity concentration at the neighborhood of respective depth thereof.

Abstract: In a trench isolation structure having active regions at a main surface of a silicon substrate isolated by providing a gate electrode on an insulation film formed in a trench with a gate oxide film thereunder, the insulation film has a vertical cross section configuration wherein the carrier concentration of the active region at the proximity of the upper edge corner of the trench becomes lower than the carrier concentration at the center of the active region in a state where a predetermined bias voltage is applied to the gate electrode. According to this structure, electric field concentration at the edge of the trench isolation can be relaxed and generation of an inverse narrow channel effect suppressed. Therefore, the subthreshold characteristics can be improved.

Abstract: There are provided a semiconductor device, which includes an element isolating oxide film having a good upper flatness, and a method of manufacturing the same. Assuming that t.sub.G represents a thickness of a gate electrode layer 6, a height t.sub.U to an upper surface of a thickest portion of element isolating oxide film 4 from an upper surface of a gate insulating film 5 and an acute angle .theta.i defined between the upper surfaces of element isolating oxide film 4 and gate insulating film are set within ranges expressed by the formula of {.theta.i, t.sub.U .linevert split.0.ltoreq..theta.i.ltoreq.56.6.degree., 0.ltoreq.t.sub.U .ltoreq.0.82t.sub.G }. Thereby, an unetched portion does not remain at an etching step for patterning the gate electrode layer to be formed later. This prevents short-circuit of the gate electrode. Since the element isolating oxide film has the improved flatness, a quantity of overetching in an active region can be reduced at a step of patterning the gate electrode.

Abstract: Reverse short-channel effect is suppressed in a field effect transistor with a gate having a short length. The field effect transistor comprises a p-type silicon substrate, a gate electrode, paired lightly doped source/drain regions, and paired heavily doped source/drain regions. A boron concentration peak region is formed in the silicon substrate. A boron concentration peak region positioned at an end of the gate electrode has a length d of one fourth of a length L of the gate electrode, and extends from the end to the center of the gate electrode.

Abstract: An impurity concentration profile that improves pn junction breakdown voltage and mitigates the electric field, and that does not adversely affect the characteristics of a field effect transistor is realized. An n type source/drain region is formed at a silicon substrate. A p type impurity concentration profile includes respective peak concentrations at a dope region for forming a p type well, a p type channel cut region, and a p type channel dope region. An impurity concentration profile of the n type source/drain region crosses the p type impurity concentration profile at a low concentration, and includes phosphorus implantation regions indicating impurity concentrations respectively higher than those of the p type channel cut region and the p type channel dope region and respective peaks in impurity concentration at the neighborhood of respective depth thereof.

Abstract: There are provided a semiconductor device, which includes an element isolating oxide film having a good upper flatness, and a method of manufacturing the same. Assuming that t.sub.G represents a thickness of a gate electrode layer 6, a height t.sub.U to an upper surface of a thickest portion of element isolating oxide film 4 from an upper surface of a gate insulating film 5 and an acute angle .theta.i defined between the upper surfaces of element isolating oxide film 4 and gate insulating film are set within ranges expressed by the formula of {.theta.i, t.sub.U .linevert split.0.ltoreq..theta.i.ltoreq.56.6.degree., 0.ltoreq.t.sub.U .ltoreq.0.82t.sub.G }. Thereby, an unetched portion does not remain at an etching step for patterning the gate electrode layer to be formed later. This prevents short-circuit of the gate electrode. Since the element isolating oxide film has the improved flatness, a quantity of overetching in an active region can be reduced at a step of patterning the gate electrode.

Abstract: An isolating/insulating film is formed on the surface of a p.sup.- silicon substrate in an element isolating region. An nMOS transistor having a pair of n-type source/drain regions is formed within an element forming region isolated by the isolating oxide film. A p.sup.+ impurity diffusion region is formed on the p.sup.- silicon substrate in such a manner as to be contacted with the lower surface of the isolating oxide film in the element isolating region and to extend at a specified depth from the surface of the p.sup.- silicon substrate in the element forming region. A p-type impurity diffusion region having a p-type impurity concentration higher than that of the p.sup.- silicon substrate is formed at the side end portion of the isolating oxide film in such a manner as to be contacted with the n-type source/drain region. With this arrangement, it is possible to reduce leakage current caused by the distribution of crystal defects in a depletion layer.