<p>This paper proposes a semi-analytical numerical method for size-dependent three-dimensional adhesive contact problems applicable to various surface geometries. The model is developed based on frequency response functions within the couple stress elasticity framework and an adhesion-extended conjugate gradient method, and employs the Maugis-Dugdale adhesion model to characterize interfacial adhesion behavior. The proposed approach provides a general tool for investigating the adhesive contact behavior of dissimilar elastic materials under the influence of size effects. A detailed parametric analysis is performed using this model to assess the influence of the shear modulus ratio, adhesion parameter, characteristic material length, and normal force on key adhesive contact responses, including pull-off force, contact radius, attraction force, contact pressure, and normal displacement. Results demonstrate that the shear modulus ratio plays a pivotal role in governing adhesive contact behavior in the case of size effects that cannot be neglected. The developed semi-analytical numerical model offers important insights into the adhesive contact mechanics of complex microstructures.</p>