A vertical insulated gate transistor is manufactured by providing a trench (26) extending through a source layer (8) and a channel layer (6) towards a drain layer (2). A spacer etch is used to form gate portions (20) along the trench side walls, a dielectric material (30) is filled into the trench between the sidewalls gate portions (20), and a gate electrical connection layer (30) is formed at the top of the trench electrically connecting the gate portions (20) across the trench.