High voltage ldmos transistor and methods for manufacturing the same

A method of fabricating a semiconductor device, comprising:

• forming a gate over a substrate, the gate having a main portion and an extension portion at one end of the main portion;
• forming a source region and a drain region in the substrate such that the gate is disposed between the source region and the drain region, and wherein a length of the source region is greater than the length of the drain region in a direction substantially perpendicular to a channel length defined between the source region and the drain region;
• and
• wherein the main portion of the gate has a first sidewall substantially perpendicular to a channel length and interposing the region and the drain region, wherein the extension portion extends from the first sidewall toward the drain region in the direction substantially parallel to the channel length;
• wherein on application of a voltage to the gate, electrons flow away from the second doped region in a the direction substantially perpendicular to the channel length and the in the direction substantially parallel to the channel length.

A method of manufacturing a MOSFET, the method comprising:

• forming a gate having a main portion and an extension portion on a substrate, wherein the main portion and the extension portion are contiguous, the main portion being rectangular and the extension portion extending from a first sidewall of the main portion in a first direction;
• forming a first doped region in the substrate on one side of the main portion of the gate, wherein the first doped region has a first length in the first direction;
• and
• forming a second doped region in the substrate on the other side of the main portion of the gate in the first direction, wherein the second doped region has a second length in the first direction, the second length greater than the first length, wherein the first doped region and the second doped region are of a same conductivity type and the main portion of the gate is between an edge of the first doped region and an edge of the second doped region.