Power MOSFETs and methods for manufacturing the same

A high voltage MOSFET, comprising:

• a well;
• a lightly doped region of a first conductivity type located at a first side within the well;
• a drain of the first conductivity type within the lightly doped region;
• a source of the first conductivity type at a second side within the well, the second side being opposite to the first side, the source comprising:
• a first source region having a first boundary facing the drain, the first boundary directly interfacing with the well;
• and
• a second source region under the first source region, having a second boundary facing the drain, the second boundary directly interfacing with the well, the first source region having a dopant different from a dopant of the second source region, and the first boundary and the second boundary being vertically aligned;
• a gate electrode over the well and between the source and the drain, the gate electrode covering a part of the lightly doped region and a part of the drain;
• and
• spacers located at both sides of the gate electrode, wherein a ratio of the width of each spacer to the width of the gate electrode is in a range from 1:4 to 1:7.

A high voltage semiconductor structure, comprising:

• a well of a first conductivity type;
• a lightly doped region of a second conductivity type located at a first side within the well, the lightly doped region comprising a first dopant concentration greater than a dopant concentration of the well;
• a drain of the second conductivity type within the lightly doped region, the drain comprising a second dopant concentration greater than the first dopant concentration;
• a source of the second conductivity type at a second side within the well region, the second side being opposite to the first side, the source comprising a third dopant concentration greater than the first dopant concentration, the source comprising:
• a first source region having a substantially vertical boundary facing the drain, the substantially vertical boundary of the first source region directly interfacing with the well;
• and
• a second source region under the first source region, having a substantially vertical boundary facing the drain, the substantially vertical boundary of the second source region directly interfacing with the well, the first source region having a dopant different from a dopant of the second source region;
• and
• a gate electrode over the well and between the source and the drain, the gate electrode covering a part of the lightly doped region and a part of the drain.