Goal of this paper is to study the following singularly perturbed nonlinear Schrödinger equation $$ \varepsilon^{2s}(- \Delta)^s v+ V(x) v= f(v), \quad x \in \mathbb{R}^N, where $s (0,1)$, $N \geq 2$, $V C(\mathbb{R}^N,\mathbb{R})$ a positive potential and $f$ assumed critical satisfying general Berestycki-Lions type conditions. When $\varepsilon>0$ small, we obtain existence multiplicity semic...