Drain extended nmos transistor

A semiconductor device, comprising:

• a substrate including a semiconductor material;
• and
• an NMOS transistor including a plurality of fingers, each finger including:
• a segment of a body region in the substrate, the segment of the body region including p-type semiconductor material;
• a segment of a body connection on the segment of the body region;
• a segment of an STI oxide layer on the substrate, the segment of the STI oxide layer laterally surrounding the segment of the body connection;
• a first segment of a source region in the substrate outside the segment of the STI oxide layer on a first side of the segment of the body connection, and a second segment of the source region in the substrate outside the segment of the STI oxide layer on a second, opposite, side of the segment of the body connection, the first segment of the source region and the second segment of the source region including n-type semiconductor material;
• a segment of a LOCOS oxide layer on the substrate, the segment of the LOCOS oxide layer laterally surrounding the first segment of the source region, the second segment of the source region, and the segment of the STI oxide layer,
• a segment of a gate dielectric layer over a portion of the segment of the body region;
• a segment of a gate over the segment of the gate dielectric layer;
• a portion of a first segment of a lightly-doped drain layer on a first side of the segment of the gate, and a portion of a second segment of the lightly-doped drain layer on a second, opposite, side of the segment of the gate, the first segment of the lightly-doped drain layer and the second segment of the lightly-doped drain layer including n-type semiconductor material;
• and
• a portion of a first drain contact region adjacent to the portion of a first segment of the lightly-doped drain layer, and a portion of a second drain contact region adjacent to the portion of a second segment of the lightly-doped drain layer.

A method of forming a semiconductor device, comprising:

• providing a substrate including a semiconductor material;
• and
• forming an NMOS transistor, comprising the steps:
• forming an STI oxide layer on the substrate, the STI oxide layer having a closed-loop configuration;
• implanting n-type dopants into the substrate to form a drift implanted layer outside of the STI oxide layer,
• forming a LOCOS oxide layer on the substrate outside of the STI oxide layer, the LOCOS oxide layer having a closed-loop configuration, the LOCOS oxide layer partially overlapping the drift implanted layer,
• diffusing and activating the n-type dopants in the drift implanted layer to form a lightly-doped drain layer extending under the LOCOS oxide layer,
• implanting p-type dopants into the substrate to form a body region extending under the STI oxide layer and partway under the LOCOS oxide layer;
• forming a gate dielectric layer on the substrate over a portion of the body region between the STI oxide layer and the LOCOS oxide layer;
• forming a gate over the gate dielectric layer, the gate extending partway over the LOCOS oxide layer;
• implanting p-type dopants to form a body connection inside the STI oxide layer on the body region;
• implanting n-type dopants into the substrate to form a source region outside of the STI oxide layer and inside the LOCOS oxide layer;
• and
• implanting n-type dopants into the substrate to form drain contact regions on the lightly-doped drain layer outside the LOCOS oxide layer.