-\varepsilon^2\Delta v+V(x)v+K(x)\phi v=|v|^{p-2}v, x in R^3,
-\varepsilon^2\Delta \phi=K(x){v}^2,                x in R^3,
where p\in(4,6), the potentials V, K\in C(R^3, R^+)  and \varepsilon>0 is a parameter. Under the critical frequency assumptions on V and K,
we investigate the existence and multiplicity  of semi-classical solutions for this system and exhibit the concentration behavior that such solutions converge to the least energy solutions of the associate limit problem as \varepsilon\rightarrow 0.