High voltage lateral semiconductor device

A high voltage lateral semiconductor device, comprising:

• a first semiconductor substrate;
• a first-conductivity-type second semiconductor substrate that is bonded to the first semiconductor substrate with an oxide film interposed therebetween, to provide a bonded substrate structure, said second semiconductor substrate being polished to have a desired thickness;
• a second-conductivity-type well region formed in a selected portion of a surface layer of the second semiconductor substrate;
• a high-impurity-concentration second-conductivity-type contact region formed in a selected portion of a surface layer of the second-conductivity-type well region;
• a first-conductivity-type source region formed in a selected portion of the surface layer of the second-conductivity-type well region, such that the source region overlaps the second-conductivity-type contact region;
• a gate electrode layer formed on a gate insulating film, over a part of the second-conductivity-type well region that is interposed between the first-conductivity-type source region and the second semiconductor substrate;
• a source electrode formed on the second-conductivity-type contact region and the first-conductivity-type source region;
• a high-impurity-concentration first-conductivity-type drain region that is formed in a selected portion of the surface layer of the second semiconductor substrate, apart from the second-conductivity-type well region;
• and
• a drain electrode formed on the first-conductivity-type drain region;
• wherein a surface pattern including the second-conductivity-type well region and the first-conductivity-type drain region is formed in an island-like shape in which one of the well region and the drain region surrounds the other thereof, or in a comb-like shape in which the well region and the drain region surround each other;
• and
• wherein the first-conductivity-type source region is not formed at a location where an edge line of the second-conductivity-type well region is opposed to an edge line of the first-conductivity-type drain region, and the length of the edge line of the second-conductivity-type well region is larger than that of the edge line of the first-conductivity-type drain region.