Semiconductor device

A semiconductor device that supplies a charging current to charge a target element, comprising:

• a semiconductor layer of a first conductivity type;
• a first semiconductor region of a second conductivity type which is formed on a main surface of the semiconductor layer and is electrically connected to a first electrode of the target element;
• a second semiconductor region of the first conductivity type which is formed on the main surface of the semiconductor layer and is arranged adjacent to the first semiconductor region;
• a third semiconductor region of the second conductivity type which is formed on a surface of the second semiconductor region and is supplied with a power supply voltage;
• a source electrode which is connected to the third semiconductor region and is supplied with the power supply voltage;
• a drain electrode which is connected to the first semiconductor region and is electrically connected to the first electrode;
• a back gate electrode which is connected to a region in the second semiconductor region separated from the third semiconductor region and is grounded;
• a gate electrode which is arranged to face a channel region located in the second semiconductor region between the third semiconductor region and the first semiconductor region with a gate insulating film interposed therebetween;
• a fourth semiconductor region of the second conductivity type which is formed in the second semiconductor region and arranged to surround the periphery of the third semiconductor region and isolate the third semiconductor region from the second semiconductor region,
• a breakdown voltage between the source electrode and the back gate electrode being greater than the power supply voltage,
• the fourth semiconductor region extends from the periphery of the third semiconductor region to a region in the second semiconductor region which is opposed to the first semiconductor region and separated from the first semiconductor region, and
• the channel region is arranged in the second semiconductor region between the fourth semiconductor region and the first semiconductor region.