A method of fabricating a semiconductor device includes providing a semiconductor substrate including a channel region, forming a gate electrode structure on the channel region of the semiconductor substrate, forming a first trench in the semiconductor substrate, and forming a second trench in the semiconductor device. The first trench may include a first tip that protrudes toward the channel. The second trench may be an enlargement of the first trench and may include a second tip that also protrudes toward the channel region. In some examples, the second tip may protrude further towards the channel region than the first tip.