How to make a model window like as a dialog box onsenUI

Question

i want to make modal window like this way http://www.w3schools.com/bootstrap/tryit.asp?filename=trybs_modal&stacked=h

Here is my controller code :

 $scope.showModal = function () {
                $scope.modalMessage="Modal Message Custom"
                modal.show();
          };

UI design :

<ons-modal var="modal">
    <h3>model message </h3>
     <ons-button onclick="modal.hide()">Close</ons-button>
</ons-modal>

this my UI Now :

but want not full screen it should be like this