A semiconductor device includes a transistor formed in a semiconductor substrate including a main surface. The transistor includes a source region, a drain region, a channel region, and a gate electrode. The source region and the drain region are disposed along a first direction, the first direction being parallel to the main surface. The channel region has a shape of a ridge extending along the first direction, the ridge including a top side and a first and a second sidewalls. The gate electrode is disposed at the first sidewall of the channel region, and the gate electrode is absent from the second sidewall of the channel region.