A method for manufacturing a semiconductor device having a vertical transistor includes forming hard masks on a semiconductor substrate to expose portions of the semiconductor substrate. Then the exposed portions of the semiconductor substrate are etched to define grooves in the semiconductor substrate. A gate conductive layer is formed on the hard masks and surfaces of the grooves to a thickness that does not completely fill the grooves. A sacrificial layer is formed on the gate conductive layer to completely fill the grooves. A partial thickness of the sacrificial layer is removed to expose the gate conductive layer and portions of the gate conductive layer formed on the hard masks and on sidewalls of upper portions of the grooves are removed. The remaining sacrificial layer is completely removed. Gates are formed on sidewalls of lower portions of the grooves by etching the gate conductive layer.