A method of manufacturing a semiconductor device includes: forming a trench extending into a semiconductor substrate and a polysilicon gate electrode in the trench; forming a body region of a first conductivity type in the substrate adjacent the trench and a source region of a second conductivity type adjacent the body region and the trench; forming a dielectric layer on the substrate; forming a gate metallization on the dielectric layer which covers part of the substrate and a source metallization on the dielectric layer which is electrically connected to the source region, spaced apart from the gate metallization and covering a different part of the substrate than the gate metallization; and forming a metal-filled groove in the polysilicon gate electrode which is electrically connected to the gate metallization. The metal-filled groove extends along a length of the trench underneath at least part of the source metallization.