Semiconductor memory device with shallow buried capacitor and fabrication method thereof

A method for forming a semiconductor device, comprising:

• providing a substrate comprising a semiconductor substrate, a buried oxide layer on said semiconductor substrate, and a silicon device layer on said buried layer;
• forming at least one bottle-shaped capacitor cavity extending through said silicon device layer and said buried oxide layer, wherein said at least one bottle-shaped capacitor cavity is comprised of an upper portion disposed in said silicon device layer and a widened bottom burrow disposed in said buried oxide layer and underneath the silicon device layer, wherein said widened bottom burrow is wider than said upper portion;
• forming at least one buried capacitor in said at least one bottle-shaped capacitor cavity, said at least one buried capacitor comprising an inner electrode and an outer electrode with a capacitor dielectric layer therebetween;
• forming a conductive material layer embedded within said upper portion, wherein said inner electrode is in direct contact with said conductive material layer;
• and
• forming at least one transistor on said substrate, wherein said at least one transistor comprises a source region and a drain region disposed in said silicon device layer, a channel region between said source region and said drain region, and a gate over said channel region, and wherein said source region is electrically connected to said inner electrode of said at least one buried capacitor.