LDMOS transistors including vertical gates with multiple dielectric sections, and associated methods

A lateral double-diffused metal-oxide-semiconductor (LDMOS) transistor, comprising:

• silicon semiconductor structure, including:
• a base layer,
• an n-type layer disposed over the base layer in a thickness direction,
• a p-body region disposed in the n-type layer,
• a source p+ region and a source n+ region each disposed in the p-body region, and
• a drain n+ region disposed in the n-type layer;
• and
• a vertical gate including:
• a gate conductor extending from a first outer surface of the silicon semiconductor structure into the silicon semiconductor structure into the n-type layer in the thickness direction and the gate conductor is disposed between the source n+ region and the drain n+ region in a lateral direction orthogonal to the thickness direction;
• and
• a gate dielectric layer including at least four dielectric sections, each of the at least four dielectric sections separating the gate conductor from the silicon semiconductor structure by a respective separation distance, wherein the at least four dielectric sections include:
• a first dielectric section separating the gate conductor from a drain portion of the n-type layer in the lateral direction by a first separation distance t1;
• a second dielectric section separating the gate conductor from a well portion of the n-type layer in the thickness direction by a second separation distance t2 different from the first separation distance t1;
• and
• a third dielectric section separating the gate conductor from the p-body region by a third separation distance t3 different from each of the first separation distance t1 and the second separation distance t2;
• a fourth dielectric section separating the gate conductor from a source portion of the n-type layer in the lateral direction by a fourth separation distance t4 that is different from each of the first separation distance t1, the second separation distance t2, and the third separation distance t3.