diff --git a/compiler/pgates/pgate.py b/compiler/pgates/pgate.py
index a7974cd2..0c1c0b52 100644
--- a/compiler/pgates/pgate.py
+++ b/compiler/pgates/pgate.py
@@ -8,7 +8,7 @@
 import contact
 import design
 import debug
-from tech import layers
+from tech import layer, drc
 from vector import vector
 from globals import OPTS
 from sram_factory import factory
@@ -141,27 +141,29 @@ class pgate(design.design):
         max_y_offset = self.height + 0.5 * self.m1_width
         self.nwell_position = middle_position
         nwell_height = max_y_offset - middle_position.y
-        if layers["nwell"]:
+        if layer["nwell"]:
             self.add_rect(layer="nwell",
                           offset=middle_position,
                           width=self.well_width,
                           height=nwell_height)
-        self.add_rect(layer="vtg",
-                      offset=self.nwell_position,
-                      width=self.well_width,
-                      height=nwell_height)
+        if layer["vtg"]:
+            self.add_rect(layer="vtg",
+                          offset=self.nwell_position,
+                          width=self.well_width,
+                          height=nwell_height)
 
         pwell_position = vector(0, -0.5 * self.m1_width)
         pwell_height = middle_position.y - pwell_position.y
-        if layers["pwell"]:
+        if layer["pwell"]:
             self.add_rect(layer="pwell",
                           offset=pwell_position,
                           width=self.well_width,
                           height=pwell_height)
-        self.add_rect(layer="vtg",
-                      offset=pwell_position,
-                      width=self.well_width,
-                      height=pwell_height)
+        if layer["vtg"]:
+            self.add_rect(layer="vtg",
+                          offset=pwell_position,
+                          width=self.well_width,
+                          height=pwell_height)
 
     def add_nwell_contact(self, pmos, pmos_pos):
         """ Add an nwell contact next to the given pmos device. """
diff --git a/compiler/pgates/ptx.py b/compiler/pgates/ptx.py
index 64e6a893..f3180840 100644
--- a/compiler/pgates/ptx.py
+++ b/compiler/pgates/ptx.py
@@ -7,7 +7,7 @@
 #
 import design
 import debug
-from tech import drc, spice
+from tech import layer, drc, spice
 from vector import vector
 from sram_factory import factory
 
@@ -319,11 +319,13 @@ class ptx(design.design):
         """
         Add an (optional) well and implant for the type of transistor.
         """
-        if drc("has_{}well".format(self.well_type)):
-            self.add_rect(layer="{}well".format(self.well_type),
+        well_name = "{}well".format(self.well_type)
+        if layer[well_name]:
+            self.add_rect(layer=well_name,
                           offset=(0,0),
                           width=self.cell_well_width,
                           height=self.cell_well_height)
+        if layer["vtg"]:
             self.add_rect(layer="vtg",
                           offset=(0,0),
                           width=self.cell_well_width,
diff --git a/technology/scn4m_subm/tech/tech.py b/technology/scn4m_subm/tech/tech.py
index 60dc8421..8d466023 100644
--- a/technology/scn4m_subm/tech/tech.py
+++ b/technology/scn4m_subm/tech/tech.py
@@ -35,8 +35,8 @@ GDS["zoom"] = 0.5
 
 # create the GDS layer map
 layer={} 
-layer["vtg"]            = (-1, 0)
-layer["vth"]            = (-1, 0)
+layer["vtg"]            = None
+layer["vth"]            = None
 layer["pwell"]          = (41, 0)
 layer["nwell"]          = (42, 0)
 layer["active"]         = (43, 0)