Method of manufacturing a semiconductor device with trench gate by using a screen oxide layer

A method of manufacturing a semiconductor device, the method comprising:

• forming a screen oxide layer on a main surface of a semiconductor layer and a passivation layer on the screen oxide layer;
• forming a gate trench in a portion of the semiconductor layer exposed by a mask opening in a trench mask comprising the passivation layer after forming the screen oxide layer;
• forming a gate dielectric at least along sidewalls of the gate trench;
• implanting, after removing the passivation layer, dopants through the screen oxide layer to form at least one of a source zone and a body zone in the semiconductor layer,
• forming, prior to forming the screen oxide layer, field plate structures extending from the main surface into the semiconductor layer, the field plate structures comprising an electrically conductive field electrode and a field dielectric that electrically insulates the field electrode from the semiconductor layer;
• and
• electrically connecting the field electrode to the source zone.