Power semiconductor device and method of manufacturing the same

A semiconductor device comprising:

• a first conductivity-type well region in a semiconductor substrate;
• a stepped field insulating layer on a surface of the first conductivity-type well region;
• a second conductivity-type body region in the first conductivity-type well region on one side of the field insulating layer;
• a gate oxide layer on the semiconductor substrate;
• a gate on the gate oxide layer adjoining the stepped field insulating layer and on part of the stepped field insulating layer;
• a source region in the second conductivity-type body;
• and
• a drain region in the first conductivity-type well on an opposite side of the field insulating layer.

A method of manufacturing a semiconductor device, comprising:

• forming a field insulating layer in a high-voltage device region of a semiconductor substrate;
• forming a first gate oxide layer on exposed surfaces of the semiconductor substrate;
• simultaneously etching part of the field insulating layer and the first gate oxide layer in the low-voltage device region to expose the semiconductor substrate in the low-voltage device region and form a stepped field insulating layer;
• forming a second gate oxide layer with the first gate oxide layer in the high-voltage device region and on the exposed semiconductor substrate in the low-voltage device region;
• and
• forming a gate over part of the stepped field insulating layer and part of the second gate oxide layer in the high-voltage device region adjoining the field insulating layer.