A transistor has a cell array with two or more transistor cells, a temperature sensor, which is integrated in the cell array or is adjacent to the cell array, and an isolation structure. The isolation structure isolates the temperature sensor from the cell array, and has an isolation trench, which is arranged between the cell array and the temperature sensor. The distance between the temperature sensor and the active transistor cell that is closest to the temperature sensor corresponds approximately to the pitch between active transistor cells within the cell array.