METHOD FOR PRODUCING SEMICONDUCTOR DEVICE

摘要

Elements are respectively formed on a semiconductor substrate in a vertical trench gate MOSFET region (21), and in a lateral planar gate MOSFET region (22) for control purposes, by first forming a trench (33) on the semiconductor substrate in the vertical trench gate MOSFET region (21). Next, a first gate oxide film (7a) is formed along the inside wall of the trench (33). Next, the interior of the trench (33) is filled with a polysilicon film (6a), with the first gate oxide film (7a) therebetween. Next, a LOCOS oxide film (11) is formed in an element isolating region. Next, a second gate oxide film (7b) is formed on the semiconductor substrate in the lateral planar gate MOSFET region (22). The advantageous effects thereof include that increase in the number of process steps is minimized, that the gate threshold voltage of the output-stage MOSFET is greater than the gate threshold voltage of the control MOSFET, that the LOCOS oxide film (11) is not too thin, and that foreign matter residue is not produced within the trench (33).