| 摘要 |
PURPOSE:To accelerate the switching speed of a semiconductor device by decreasing the impurity density of a depletion type load MOSFET substrate region lower than that for determining the characteristics of an enhancement type drive MOSFET. CONSTITUTION:An SiO2 film 22 and an Si3N4 film 23 are coated on a P<->-type Si substrate 21, a resist film 24 is coated on the MOSFET forming region, the film 23 around the film 24 is etched and removed, ion is implanted through the film 22 thus exposed to form a P<+>-type region 25 thereon. Then, the film 24 is modified to a film 26 for coating the depletion type region, a P<+>-type ion implanted region 27 is formed in the enhancement type region, the film 26 is removed, and a thick field SiO2 film 221 is formed on the periphery thereof. Thereafter, a P-type layer 28 for preventing leakage of a current is formed on the surface layer of the substrate 21, a resist film 29 is coated on the enhancement type region, an N<->-type ion implanted region 30 is formed on the depletion type region, and a deep N<+>-type region 32 is formed between the two type regions to reduce the resistance. |
