SUPERJUNCTION TRANSISTOR DEVICE AND METHOD FOR FORMING A SUPERJUNCTION TRANSISTOR DEVICE

A method for forming a drift region of a superjunction transistor and a superjunction transistor device are disclosed. The method includes forming a plurality of first regions (21) of a first doping type and a plurality of second regions (22, 23) of a second type in a semiconductor body (100) such that the first regions (21) and the second regions (22, 23) are arranged alternatingly in the semiconductor body (100), wherein forming the first regions (21) and the second regions (22, 23) Includes: forming a plurality of trenches (131) in at least one semiconductor layer (130); implanting first type dopant atoms and second type dopant atoms into each of opposing sidewalls (133, 134) of the plurality of trenches (131); filling the plurality of trenches (131) with a semiconductor material; and diffusing the first type dopant atoms and second type dopant atoms in a thermal process so that first type dopant atoms form the first regions (21) and second type dopant atoms form the second regions (22, 23). Each of the plurality of trenches (131) has a first width (w131), the trenches (131) are separated by mesa regions (135) each having a second width (w135), and the first width (w131) is greater than the second width (w135).