Physical quantity sensor having protrusion and method for manufacturing the same

A physical quantity sensor for detecting a physical quantity, the sensor comprising:

• a movable portion having a bottom;
• and
• a protrusion disposed on the bottom of the movable portion;
• a fixed electrode;
• and
• a substrate for supporting the movable portion movably,
• wherein the movable portion includes a movable electrode, which faces the fixed electrode in a horizontal direction so that the movable electrode is separated from the fixed electrode by a predetermined distance,
• wherein the protrusion is provided by a remaining portion, which remains without being etched when the movable portion is prepared by etching,
• wherein the movable portion is disposed over the substrate with a predetermined clearance therebetween,
• wherein the protrusion protrudes toward the substrate so that the protrusion prevents the movable portion from adhering to the substrate,
• wherein the movable portion includes a part, which has a large width compared with other parts of the movable portion, so that the part protrudes from the other parts toward the fixed electrode,
• wherein the part prevents the movable electrode from adhering to the fixed electrode,
• wherein the protrusion is disposed on the bottom of the part, and
• wherein the protrusion is formed simultaneously together with the movable portion in a case where the movable portion is removed from the substrate by etching.