In this paper, four different designs for a new three-axes monolithic low-g
acceleration sensor are presented. The silicon spring-mass system of the s
ensor is fabricated in a single step by anisotropic wet chemical etching in
KOH using (111) planes as physical etch stop. The orientation of the suppo
rting beams of the spring-mass systems allows the seismic mass to move in a
direction orthogonal to the (111) planes. Four mass-spring systems, each o
ne rotated by 90 degrees, enables the detection of three components of the
acceleration vector using capacitive readout. Two alignment structures are
presented meeting the high requirements in terms of mask alignment, which a
re necessary when using the described etch technique. A new space saving co
mpensation structure protecting the convex edges of the seismic masses duri
ng the etch process was realized and compared with standard solutions. The
sensors performance was characterized and is demonstrated.