DMOS fabrication process implemented with reduced number of masks

A method for fabricating a DMOS transistor supported on a substrate comprising steps of:

• (a) growing an oxide layer on said substrate;
• (b) applying a first mask for removing said oxide layer to define an active area and for selectively patterning said oxide layer for keeping a plurality of source implant blocking stumps near a plurality of source regions in said substrate wherein said blocking stumps being formed with width greater than twice a diffusion length of a source dopant;
• (c) applying a trench mask to form a plurality of trenches on said substrate between said blocking stumps followed by forming a plurality of gates in said trenches;
• (d) implanting a body dopant through said implant window followed by a body diffusion for forming body regions underneath said blocking stumps wherein said blocking stumps are patterned with width less than twice a diffusion length of said body dopant whereby said body regions merge together in said body diffusion and become a single body region underneath said blocking stumps;
• and
• (e) implanting said source dopant through said implant window over said source implant blocking stumps following by a source diffusion for forming separate source regions underneath said blocking stumps;
• applying a trench mask to form a plurality of trenches on substrate between said blocking stumps followed by forming a plurality of gates in said trenches.

A method for fabricating a trenched DMOS transistor supported on a substrate comprising steps of:

• (a) growing an oxide layer on said substrate;
• (b) applying a first mask for removing said oxide layer to define an active area and for selectively patterning said oxide layer for keeping a plurality of source implant blocking stumps near a plurality of source regions in said substrate wherein said blocking stumps being formed with width greater than twice a diffusion length of a source dopant;
• (c) applying a second mask for forming a plurality of trenches between said blocking stumps and forming gates in said trenches thus defining a plurality of implant windows between said gates and said blocking stumps;
• (d) implanting a body dopant through said implant windows followed by a body diffusion for forming body regions underneath said blocking stumps;
• and
• (e) implanting said source dopant through said implant windows over said source implant blocking stumps following by a source diffusion for forming separate source regions underneath said blocking stumps.