Shielded gate trench mosfet with esd diode manufactured using two poly-silicon layers process

A SGT MOSFET comprising:

• an epitaxial layer of a first conductivity type extending over a substrate;
• a plurality of first type trenches formed in said epitaxial layer in an active area, each of said first type trenches being filled with a shielded gate structure comprising a first poly-silicon layer in a lower portion to serve as a shielded electrode and a second poly-silicon layer in an upper portion to serve as a gate electrode, wherein said shielded electrode is insulated from said epitaxial layer by a first insulating film and said gate electrode is insulated from said epitaxial layer by a gate insulating film which has a thickness less than said first insulating film, wherein said shielded electrode and said gate electrode are insulated from each other by a second insulating film;
• an ESD clamp diode made of said second poly-silicon layer formed on top of said epitaxial layer and multiple second type trenches, wherein each of said second type trenches is filled with said first poly-silicon layer as a lower electrode and said second poly-silicon layer as an upper electrode, wherein said upper electrode is isolated from said lower electrode by said second insulating film;
• said ESD clamp diode being isolated from said epitaxial layer by said gate insulating film, said lower electrode being isolated from said epitaxial layer by said first insulating film;
• said first and second poly-silicon layers being doped with said first conductivity type;
• and
• trenched anode (cathode) contacts of said ESD clamp diode being located in said upper electrode.