A method of manufacturing a semiconductor device includes forming trenches in a first conductivity type semiconductor layer. An insulating film is then formed to cover the inner surfaces of the trenches. A part of the insulating film which is covering a bottom part of the trenches is removed from at least a portion of the trenches. Dopant ions are implanted into regions of the semiconductor layer that are below the bottom parts of that portion of the trenches from which the portion of the insulating film has been removed.