Semiconductor device having an insulator including an inductive load driving circuit

A synchronous buck DC-DC converter comprising:

• a semiconductor substrate of a first conductivity type;
• a first line supplying a first voltage;
• an inductor element;
• a second line supplying a second voltage lower than the first voltage;
• a first switching element formed on the semiconductor substrate and connected between the first line and one end of the inductor;
• a second switching element formed on the semiconductor substrate and connected between the one end of the inductor and the second line;
• a controller formed on the semiconductor substrate and configured to control the conduction of the first and second switching elements;
• and
• a first trench formed on the semiconductor substrate to electrically separate the second switching element from the first switching element and the controller,
• the second switching element further including:
• a well layer of the first conductivity type selectivity formed on the semiconductor substrate;
• a first diffused layer of a second conductivity type selectivity formed on the well layer;
• a second diffused layer of the second conductivity type formed on the well layer apart from the first diffused layer;
• a control electrode formed on an insulating film between the first diffused layer and the second diffused layer;
• and
• a main electrode formed on each of the first diffused layer and the second diffused layer,
• the first trench further including a third diffused layer of the second conductivity type formed contacting to the first trench,
• the second diffused layer and the third diffused layer being electrically kept at the same potential.