Patent ID: 7714370

Claim:
A semiconductor storage device comprising: a semiconductor substrate having a supporting substrate, a buried oxide film on the supporting substrate, and an SOI layer on the buried oxide film; an element isolating layer insulating and isolating the SOI layer at a transistor forming region and a capacitor forming region which are set at the semiconductor substrate; a MOSFET on the SOI layer of the transistor forming region; and a MOS capacitor on the SOI layer of the capacitor forming region, wherein the MOSFET includes a gate insulating film on the SOI layer, a floating gate electrode on the gate insulating film, a source layer and a drain layer at the SOI layer at respective sides of the floating gate electrode, a channel region between the source layer and the drain layer, a high-concentration diffusion layer at the source layer in a vicinity of an interface between the source layer and the channel region, and which contacts the channel region, the high-concentration diffusion layer having impurities of a same type and higher concentration as impurities in the channel region, and a silicide layer covering the high-concentration diffusion layer and the source layer, and the MOS capacitor includes a capacitor electrode at the SOI layer, the capacitor electrode having impurities of a same type as the source layer at a high concentration, the capacitor electrode of the MOS capacitor is disposed so as to oppose an end portion of the floating gate electrode of the MOSFET, with the gate insulating film therebetween, the capacitor electrode having a projecting portion including an inclined surface sloped toward the buried oxide film and that is provided at a side end portion of the capacitor electrode near the floating gate electrode, and a distal end of the projecting portion opposes the floating gate electrode, wherein a trench that extends into the buried oxide film is disposed between the distal end of the projecting portion and the floating gate electrode, the gate insulating film is within the trench.