Patent ID: 7418864
Filing Date: 2008-09-02
Classification: B81B,G01P

Abstract:
1. An acceleration sensor comprising: a semiconductor substrate including a support layer and a semiconductor layer, which are stacked in a first direction perpendicular to the semiconductor substrate; a movable electrode and a fixed electrode disposed in the semiconductor layer; and a trench disposed on the semiconductor layer and reaching the support layer, wherein the movable electrode separately faces the fixed electrode by sandwiching the trench along a second direction, which is parallel to the semiconductor substrate, the trench has a detection distance in the second direction, the movable electrode is movable along the first direction when acceleration is applied to the semiconductor substrate along the first direction so that the acceleration is detected on the basis of capacitance change of a capacitor between the movable electrode and the fixed electrode, the movable electrode has a bottom, which faces the support layer and is apart from the support layer, the movable electrode has a width along the second direction, and the fixed electrode has a width along the second direction, the width of the movable electrode is smaller than the width of the fixed electrode, the movable electrode has a thickness along the first direction, and the fixed electrode has a thickness along the first direction, and the thickness of the movable electrode is smaller than the thickness of the fixed electrode, the movable electrode includes a first movable portion, a second movable portion, a connection portion, and a spring, the connection portion connects between the first movable portion and the second movable portion, the connection portion is supported on the support layer through the spring, the first movable portion is disposed on an opposite side of the second movable portion through the spring as a center, the first movable portion and the second movable portion are capable of displacing with a see-saw mechanism by the spring so that a movable direction of the first movable portion is opposite to a movable direction of the second movable portion, the first movable portion and the fixed electrode provide a first capacitance, and the second movable portion and the fixed electrode provide a second capacitance, the acceleration is detected on the basis of capacitance change of a difference between the first capacitance and the second capacitance, the movable electrode further includes a weight portion, the weight portion is disposed on one side of the connection portion, the weight portion promotes the see-saw mechanism, the movable electrode further includes a capacitance compensation portion, which is disposed on the other side of the connection portion so that the capacitance compensation portion is opposite to the weight portion, and the capacitance compensation portion compensates a capacitance, which is provided by the weight portion.