When referring back to FIGS. 11A and 11B, the gate trench in the stripe design would run along the longitudinal extension of the cell mesa region, i.e. in the vertical direction of FIG. 11A, and would therefore have a length a per unit cell. Different thereto, the gate trench surrounds the spicular trench 130 in the needle trench design, which is illustrated in FIG. 11B in the left lower corner. Depending on the specific location of the gate trench in the cell mesa region, the gate trench can have a length of up to 2·a. Therefore, the channel length per unit cell area can be much larger in the needle trench design relative to the stripe design. This further reduces the on-state resistance R_ON.

FIG. 3 illustrates a vertical cross-section through a portion of the semiconductor device according to an embodiment. The vertical cross-section shown in FIG. 3 contains portion of the active cell area 105, of the transition area 106 and of the edge termination area 110. As illustrated in FIG. 3, spicular trenches 130 can be formed in any of the active cell area 105, the transition area 106, and the edge termination area 110. For example, the spicular trenches 130 can be formed at a given pattern throughout the semiconductor substrate 100. Typically, the spicular trenches 130 are arranged with the same pattern in the active cell area 105, the transition area 106 and the edge termination area 110. It would, however, also be possible to arrange the spicular trenches 130 with different patterns in, for example, the active area 104 and the edge termination area 110.