Silicon carbide semiconductor device and method of manufacturing the same

A method of manufacturing a silicon carbide semiconductor device having an inversion type vertical switching element with a trench gate structure, the silicon carbide semiconductor device including:

• a substrate of a first or second conductivity type which is made of silicon carbide, a main surface of which is a (0001) plane or a (000-1) plane, or has an off angle with respect to the (0001) plane or the 000-1) plane;
• a drift layer formed on the substrate, and made of silicon carbide of the first conductivity type which is lower in impurity concentration than the substrate;
• a base region formed on the drift layer, and made of silicon carbide of the second conductivity type;
• a source region formed on an upper portion of the base region, and made of silicon carbide of the first conductivity type which is higher in concentration than the drift layer;
• a trench that is formed from a surface of the source region to a depth reaching the drift layer through the base region, and a side wall surface of which is formed toward a (11-20) plane or a (1-100) plane;
• a gate insulating film formed on an inner wall surface of the trench;
• a gate electrode formed on the gate insulating film within the trench;
• a source electrode electrically connected to the source region and the base region;
• and
• a drain electrode formed on a rear surface side of the substrate,
• wherein an applied voyage to the gate electrode is controlled to form a channel region of the inversion type on a surface portion of the base region located on a side surface of the trench, and a current is allowed to flow between the source electrode and the drain electrode through the source region and the drift layer,
• the method of manufacturing the silicon carbide semiconductor device comprising:
• (a) forming the trench by etching;
• (b) performing sacrificial oxidation by forming a sacrificial oxide film and removing the sacrificial oxide film after forming the trench and prior to and without any step removing damage formed in the step (a);
• (c) performing a damage removing step to remove damage formed during the step (a) of forming the trench by etching, the damage removing step including chemical dry etching using a gas containing CF4 and O2 to remove the damage resulting from the step (a);
• and
• (d) forming the gate insulating film on the surface of the trench without performing sacrificial oxidation after removing the damage,
• wherein the steps (a), (b), (c) and (d) are carried out in sequence without any intervening processing steps.