Semiconductor device

1. A semiconductor device comprising:

a substrate;

a first circuit region which is formed in the substrate and in which a first circuit whose power supply potential is a first voltage is formed;

a separation region which surrounds the first circuit region;

a second circuit region which is formed in the substrate and located outside the separation region in plan view and in which a second circuit whose power supply potential is a second voltage lower than the first voltage is formed; and

a transistor which is located in the separation region and couples the second circuit to the first circuit and whose source and drain are of a first conductivity type,

the separation region comprising:

an element separation film which is formed in the substrate;

a first field plate which overlaps with the element separation film in plan view and is provided in a repetitive fashion along an edge of the first circuit region;

a plurality of conductive films which are provided over the first field plate;

a second conductivity type region which is provided in the substrate, overlaps with the element separation film in plan view, and is located around the transistor; and

a first conductivity type region which is located opposite to the source or drain of the transistor across the second conductivity type region,

wherein in a region where a portion, of the second conductivity type region, extending from a first circuit region side toward a second circuit region side and the element separation film formed in the substrate overlap each other in plan view, the first field plate and the conductive films are provided alternately from the first circuit region side toward the second circuit region side in plan view,

wherein there is a decrease in a potential of the first field plate and potentials of the conductive films from the first circuit region toward the second circuit region, and

wherein at least one of the conductive films has a potential lower than the potential of the first field plate adjacent to the conductive film on the second circuit region side in plan view, and covers at least a part of the second conductivity type region without space in an extension direction of the second conductivity type region.

2. The semiconductor device according to claim 1 ,

wherein a voltage of a drain electrode of the transistor or a voltage of another electrode in the first circuit region is applied to the first field plate on the first circuit region side,

wherein a ground potential or the second voltage is applied to the first field plate on the second circuit region side, and

wherein between the first field plate to which the voltage of the drain electrode is applied and the first field plate to which the ground potential or the second voltage is applied, the potential of the first field plate and the potentials of the conductive films are equal to or higher than the ground potential or the second voltage and are equal to or lower than the voltage of the drain electrode.

3. The semiconductor device according to claim 1 ,

wherein the conductive film is electrically coupled through a via to either of the first field plate adjacent to the conductive film on the first circuit region side in plan view and the first field plate adjacent to the conductive film on the second circuit region side in plan view.

4. The semiconductor device according to claim 3 ,

wherein the conductive film is electrically coupled through the via to the first field plate adjacent to the conductive film on the second circuit region side in plan view.

5. The semiconductor device according to claim 1 ,

wherein at least two conductive films adjacent to each other are coupled to each other, are electrically coupled through a via to the first field plate overlapping with the conductive films in plan view, and cover at least a part of the second conductivity type region between the first field plate coupled to the conductive films and an adjacent first field plate on the first circuit region side without space in the extension direction of the second conductivity type region.

6. The semiconductor device according to claim 1 ,

wherein the first field plate is provided in a repetitive folded or spiral fashion along the edge of the first circuit region, is electrically coupled to a drain electrode of the transistor or another electrode in the first circuit region at an innermost periphery, and is coupled to a ground potential or the second circuit at an outermost periphery.

7. The semiconductor device according to claim 1 , wherein adjacent first field plates are electrically floating to each other.

8. The semiconductor device according to claim 1 ,

wherein the conductive films are spaced apart from each other, and covered with a semi-insulating film.

9. The semiconductor device according to claim 1 ,

wherein the conductive films are part of a second field plate located over the first field plate, and

wherein the second field plate overlaps with the element separation film in plan view, is provided in a repetitive folded or spiral fashion along the edge of the first circuit region, is electrically coupled to a drain electrode of the transistor or another electrode in the first circuit region at an innermost periphery, and is coupled to a ground potential or the second circuit at an outermost periphery.