In this work we study the semilinear wave equation of the form u tt = u xx + λ/(1 − u) 2 , with homogeneous Dirichlet boundary conditions and suitable initial conditions, which, under appropriate circumstances, serves as a model of an idealized electrostatically actu-ated MEMS device. First we establish local existence of the solutions of the problem for any λ > 0. Then we focus on the singular behaviour of the solution, which occurs through finite-time quenching, i.e. when ||u(·, t)|| ∞ → 1 as t → t * − < ∞, investigating both conditions for quenching and the quenching profile of u. To this end, the non-existence of a regular similarity solution near a quenching point is first shown and then a formal asymptotic expansion is used to determine the local form of the solution. Finally, using a finite difference scheme, we solve the problem numerically, illustrating the preceding results.