A vertical bipolar junction transistor, comprising: a collector having a collector contact, wherein the collector contact is positioned laterally towards a first side of the transistor; a base having a base contact, wherein the base contact is positioned laterally towards a second side of the transistor, opposite the first side; an emitter having an emitter contact, wherein the emitter contact is laterally arranged to be positioned between the collector contact and the base contact; and a charge control structure (1001, 1002) configured to control a charge distribution in the collector to control a breakdown voltage of the bipolar junction transistor, wherein the charge control structure comprises: a first field plate, extending laterally over, and electrically insulated from, an upper surface of the collector; and a second field plate, extending vertically adjacent to, and electrically insulated from, a first side of the collector positioned towards the second side of the transistor, wherein the first field plate extends from the base towards the collector contact, which is positioned towards the first side of the transistor, wherein the bipolar junction transistor further comprises a trench structure adjacent the first side of the collector, which is positioned towards the second side of the transistor, the second field plate forming part of the trench structure, and wherein the trench structure is configured to be aligned under the base contact. a collector having a collector contact, wherein the collector contact is positioned laterally towards a first side of the transistor; a base having a base contact, wherein the base contact is positioned laterally towards a second side of the transistor, opposite the first side; an emitter having an emitter contact, wherein the emitter contact is laterally arranged to be positioned between the collector contact and the base contact; and a charge control structure (1001, 1002) configured to control a charge distribution in the collector to control a breakdown voltage of the bipolar junction transistor, wherein the charge control structure comprises: a first field plate, extending laterally over, and electrically insulated from, an upper surface of the collector; and a second field plate, extending vertically adjacent to, and electrically insulated from, a first side of the collector positioned towards the second side of the transistor, wherein the first field plate extends from the base towards the collector contact, which is positioned towards the first side of the transistor, wherein the bipolar junction transistor further comprises a trench structure adjacent the first side of the collector, which is positioned towards the second side of the transistor, the second field plate forming part of the trench structure, and wherein the trench structure is configured to be aligned under the base contact. a first field plate, extending laterally over, and electrically insulated from, an upper surface of the collector; and a second field plate, extending vertically adjacent to, and electrically insulated from, a first side of the collector positioned towards the second side of the transistor, wherein the first field plate extends from the base towards the collector contact, which is positioned towards the first side of the transistor, wherein the bipolar junction transistor further comprises a trench structure adjacent the first side of the collector, which is positioned towards the second side of the transistor, the second field plate forming part of the trench structure, and wherein the trench structure is configured to be aligned under the base contact.