Metal-oxide semiconductor field-effect transistor having enhanced high-frequency performance

A laterally-diffused metal-oxide semiconductor (LDMOS) device, comprising:

• a semiconductor substrate of a first conductivity type;
• a doped drift region of a second conductivity type formed on at least a portion of the substrate, the second conductivity type being opposite in polarity to the first conductivity type;
• a body region of the first conductivity type formed in the doped drift region proximate an upper surface of the doped drift region;
• source and drain regions of the second conductivity type formed proximate an upper surface of the body region and doped drift region, respectively, and spaced apart laterally from one another;
• a gate structure comprising a control gate and a field plate, the control gate being formed over at least a portion of the body region, the field plate being formed over at least a portion of the doped drift region, the gate structure being disposed between the source and drain regions and electrically isolated from the body and doped drift regions by a first insulating layer formed between the gate structure and the body and doped drift regions;
• an oxide structure formed on a portion of the doped drift region and a first portion of an upper surface of the field plate;
• and
• a silicide layer formed on a second portion of the upper surface of the field plate that is uncovered by the oxide structure,
• wherein the oxide structure is vertically non-overlapping with the drain region, and
• wherein the control gate and the field plate are formed substantially planar relative to one another such that an upper surface of the control gate is coplanar with the first portion of the upper surface of the field plate covered by the oxide structure.

A method of fabricating a laterally-diffused metal-oxide semiconductor (LDMOS) device, the method comprising:

• forming a doped drift region of a first conductivity type on at least a portion of a semiconductor substrate of a second conductivity type, the second conductivity type being opposite in polarity to the first conductivity type;
• forming a body region of the second conductivity type in the doped drift region proximate an upper surface of the doped drift region;
• forming source and drain regions of the first conductivity type proximate an upper surface of the body region and doped drift region, respectively, and spaced apart laterally from one another;
• forming a gate structure comprising a control gate and a field plate, the control gate being formed over at least a portion of the body region, the field plate being formed over at least a portion of the doped drift region, the gate structure being disposed between the source and drain regions and electrically isolated from the body and doped drift regions by a first insulating layer formed between the gate structure and the body and doped drift regions;
• and
• forming an oxide structure on a portion of the field plate and a portion of the doped drift region, the oxide structure extending on an upper surface of the field plate and overlapping a corner of the field plate,
• wherein the oxide structure is vertically non-overlapping with the drain region, and
• wherein a continuous portion of the oxide structure extends from the field plate onto the doped drift region toward the drain region, a bottom surface of the continuous portion is in direct contact with a portion of the doped drift region having a first conductivity type doping concentration less than a first conductivity type doping concentration of the drain region, and the bottom surface of the continuous portion is free of direct contact with an isolation structure.