Power semiconductor switching element

A semiconductor element comprising:

• a semiconductor substrate of a first conductivity type having a first major surface and a second major surface opposing the first major surface;
• a drift layer of the first conductivity type formed on the first major surface of said semiconductor substrate;
• a well layer of a second conductivity type selectively formed in a surface of said drift layer;
• a first trench formed to reach at least an inside of said drift layer through said well layer;
• a buried electrode formed in said first trench through a first insulating film;
• a source layer of the first conductivity type selectively formed in a surface of said well layer between said first trenches;
• a second trench formed to reach an inside of said drift layer from a surface of said source layer through said well layer;
• a control electrode formed in said second trench through a second insulating film;
• a first main electrode formed on the second major surface of said semiconductor substrate;
• and
• a second main electrode connected to said source layer and said well layer.