Method of manufacturing semiconductor device and semiconductor device

A method of manufacturing a semiconductor device having an active portion and a peripheral portion outside the active portion and having elements of an IGBT formed in the active portion, the method comprising the steps of:

• (a) preparing a substrate exhibiting n-type conductivity type that is to serve as a base layer of the IGBT;
• (b) forming a first insulating film on a main surface of the substrate, the first insulating film including a plurality of thick-film portions having a first thickness and a plurality of thin-film portions having a second thickness smaller than the first thickness;
• (c) forming a spacing portion in the thin-film portion of the first insulating film, the spacing portion reaching the substrate;
• (d) forming a surface semiconductor layer exhibiting n-type conductivity type on the thin-film portion of the first insulating film by burying the spacing portion, the surface semiconductor layer having a thickness of 20 to 100 nm;
• (e) forming a channel layer exhibiting p-type conductivity type of the IGBT in the surface semiconductor layer of the active portion;
• (f) forming an emitter layer exhibiting p-type conductivity type of the IGBT in the surface semiconductor layer of the active portion so that the emitter layer is in contact with the channel layer, the emitter layer having a higher concentration than the channel layer;
• (g) forming a gate insulating film of the IGBT on a surface of the surface semiconductor layer of the active portion;
• (h) forming a gate electrode of the IGBT on the gate insulating film;
• (i) introducing an impurity exhibiting n-type conductivity type into the surface semiconductor layer of the active portion to form a source layer of the IGBT in the surface semiconductor layer on both sides of the gate electrode;
• (j) forming an interlayer insulating film on the main surface of the substrate, the interlayer insulating film composed of a first oxide film, a nitride film, and a second oxide film;
• (k) forming a second nitride film and a fifth oxide film from the bottom from the bottom on the main surface of the substrate;
• (l) etching the fifth oxide film with using the second nitride film as an etching stopper and then sequentially etching the second nitride film and with using the spacer and the third oxide film as etching stoppers;
• (m) etching the spacer and the third oxide film to form an opening reaching the emitter layer and the source layer;
• (n) forming an emitter electrode of the IGBT on the emitter layer and the source layer, the emitter electrode electrically connected to the emitter layer and the source layer;
• (o) reducing the thickness of the substrate from a back surface to form the base layer of the IGBT;
• (p) forming an buffer layer exhibiting n-type conductivity type of the IGBT on the back surface of the substrate;
• (q) forming a collector layer exhibiting p-type conductivity type of the IGBT on the back surface of the substrate;
• and
• (r) forming a collector electrode of the IGBT electrically connected to the collector layer.