Method of manufacturing semiconductor device and semiconductor device

A method of manufacturing a semiconductor device having a shield gate structure where a gate electrode and a shield electrode are separated from each other in an in-plane direction, the method comprising in the following order:

• a semiconductor base body preparing step of preparing a semiconductor base body having a first conductive-type first semiconductor layer and a first conductive-type second semiconductor layer having lower concentration than the first semiconductor layer;
• a first trench forming step of forming a predetermined first trench on the second semiconductor layer;
• a first insulation film forming step of forming a first insulation film such that the first insulation film is filled in a lower portion of the first trench;
• a gate insulation film forming step of forming a gate insulation film on a side wall of an upper portion of the first trench;
• a gate electrode forming step of forming the gate electrode made of polysilicon with the gate insulation film interposed between the upper portion of the first trench and the gate electrode;
• a second trench forming step of forming a second trench in the inside of the first trench by removing a center portion of the first insulation film by etching;
• a second insulation film forming step of forming a second insulation film in at least the inside of the second trench under a condition that a gap remain in the inside of the second trench;
• a shield electrode forming step of forming the shield electrode in the inside of the gap;
• and
• a source electrode forming step of forming a source electrode such that the source electrode is electrically connected to the shield electrode.