A semiconductor device includes a first semiconductor region of a second conductivity type selectively formed in the main surface of the semiconductor substrate of a first conductivity type so as to be between a front surface structure of a first semiconductor element and a front surface structure of a second semiconductor element and so as to surround the front surface structure of the first semiconductor element and the front surface structure of the second semiconductor element; a second semiconductor region of the first conductivity type in the main surface of the semiconductor substrate outside the first semiconductor region and separated therefrom; and at least one trench filled with an insulating layer in the first semiconductor region between the first semiconductor element and the second semiconductor element, forming an isolation structure isolating the front surface structure of the first semiconductor element from the front surface structure of the second semiconductor element.