Method for inspecting semiconductor device

A method for inspecting a semiconductor device, the semiconductor device comprising:

• a semiconductor substrate having a first main surface and a second main surface opposite the first main surface;
• a source region formed on a side of the first main surface in the semiconductor substrate;
• a drain region formed on a side of the second main surface in the semiconductor substrate;
• a trench penetrating through the source region and formed so as to reach a predetermining depth toward the second main surface from the first main surface;
• a gate electrode formed in the trench and electrically insulated from the source region and the drain region;
• a field plate electrode formed the side of the second main surface with respect to the gate electrode and electrically insulated from the source region, the drain region, and the gate electrode in the trench;
• a source electrode electrically connected to the source region;
• and
• a drain region electrically connected to the drain region,
• wherein a second inspection includes:
• fixing the source electrode and the drain electrode to a ground potential;
• applying a second offset voltage to the gate electrode;
• applying a second screening voltage to the field plate electrode;
• and
• thereby inspecting insulation properties between the drain region and the field plate electrode and insulation properties between the gate electrode and the field plate electrode.