A semiconductor device and method of manufacturing the device is disclosed. In one aspect, the device includes a semiconductor substrate and a GaN-type layer stack on top of the semiconductor substrate. The GaN-type layer stack has at least one buffer layer, a first active layer and a second active layer. Active device regions are definable at an interface of the first and second active layer. The semiconductor substrate is present on an insulating layer and is patterned to define trenches according to a predefined pattern, which includes at least one trench underlying the active device region. The trenches extend from the insulating layer into at least one buffer layer of the GaN-type layer stack and are overgrown within the at least one buffer layer, so as to obtain that the first and the second active layer are continuous at least within the active device regions.