Semiconductor physical quantity sensor

A semiconductor physical quantity sensor comprising:

• a supporting substrate;
• a movable portion supported on the supporting substrate and having a weight portion movable in a displacement direction, and first movable electrodes and second movable electrodes provided on both sides of the weight portion and protruding from the weight portion perpendicularly to the displacement direction;
• a fixed portion provided on the supporting substrate and electrically divided from the moving portion by a trench, the fixed portion having first fixed electrodes and second fixed electrodes respectively protruding toward the movable portion and extending in parallel with the first movable electrodes and second movable electrodes and defining first and second detection intervals at the both sides of the weight portion;
• wherein an applied physical quantity is detected based on changes in capacitances generated between the first movable electrodes and the first fixed electrodes and between second movable electrodes and the second fixed electrodes when the first movable electrodes and second movable electrodes move responsive to the applied physical quantity;
• wherein an electrostatic attracting forces generated between the first movable electrodes and the first fixed electrodes act in a direction opposite to that in which electrostatic attracting forces generated between the second movable electrodes and the second fixed electrodes act;
• wherein:
• the first movable electrodes are composed of a plurality of movable electrode members;
• the first fixed electrodes are composed of a plurality of fixed electrode members opposing the plurality of movable electrode members, the plurality of fixed electrode members define the first detection intervals with the plurality of movable electrode members and define non-detection intervals with the plurality of movable electrode members, whereby the plurality of movable electrode members are disposed with the plurality of fixed electrode members interposed therebetween;
• the plurality of fixed electrode members or the plurality of movable electrode members have respective first protrusions protruding in the first detection interval;
• and
• the plurality of fixed electrode members or the plurality of movable electrode members have respective second protrusions protrusion providing in the non-detection interval.

A semiconductor physical quantity sensor comprising:

• a supporting substrate;
• a movable portion having a weight portion and movable electrode members provided on both sides of the weight portion, the weight portion including side portions positioned in a displacement direction thereof;
• a fixed portion electrically divided from the moving portion, the fixed portion having fixed electrode members each opposing each of the movable electrode members to form capacitors;
• anchor portions disposed in the displacement direction of the weight portion for anchoring end portions of the weight portion;
• suspension portions each connected to respective ones of the anchor portions and suspending the weight portion at the end portions of the weight portion in the displacement direction, each suspension portion having a spring function which enables the weight portion to move along the displacement direction;
• wherein the end portions of the weight portion along the displacement direction face to the anchor portions with intervals narrower than first detection intervals disposed between the first movable electrodes and the first fixed electrodes;
• wherein a middle part of each suspension portion is folded a plurality of times to have a plurality of folded-back portions at the outside of the weight portion or the anchor portions with respect to the displacement direction;
• wherein each of the anchor portions has a portion opposed to the weight portion directly;
• and
• said portion works as a stopper to prevent an excessive displacement of the weight portion.

A semiconductor physical quantity sensor comprising:

• a supporting substrate;
• a movable portion disposed on the supporting substrate and movable in a displacement direction, the movable portion having a weight portion, and first movable electrodes and second movable electrodes protruding from first and second sides of the weight portion and extending perpendicularly to the displacement direction;
• first fixed electrodes and second fixed electrodes fixed on the supporting substrate, electrically isolated from the movable portion, and extending in parallel with the first movable electrodes to interpose each of the first movable electrodes between each of the first fixed electrodes and each of the second fixed electrodes, the first fixed electrodes define detection intervals with the first movable electrodes to form first capacitances that are changed when a physical quantity is applied to the weight portion, the second fixed electrodes define non-detection intervals with the first movable;
• third fixed electrodes and fourth fixed electrodes fixed on the supporting substrate, electrically isolated from the movable portion, and extending in parallel with the second movable electrode to interpose each of the second movable electrodes between each of the third fixed electrodes and each of the fourth fixed electrodes, the third fixed electrodes define detection intervals with the second movable electrodes to form second capacitances that are changed in an opposite direction of the first capacitances when the physical quantity is applied to the weight portion;
• and
• first and second stoppers respectively provided in the detection intervals between the first fixed electrodes and the first movable electrodes and in the non-detection electrodes between the second fixed electrodes and the first movable electrodes, for preventing the first movable electrodes from contacting the first electrodes or the second fixed electrodes, wherein:
• each of the first and second stoppers is a protrusion protruding from one of the first fixed electrodes and the second fixed electrodes and the first movable electrodes.